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An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through
audio signal processing Audio signal processing is a subfield of signal processing that is concerned with the electronic manipulation of audio signals. Audio signals are electronic representations of sound waves— longitudinal waves which travel through air, consist ...
. Common effects include distortion/overdrive, often used with electric guitar in
electric blues Electric blues refers to any type of blues music distinguished by the use of electric amplification for musical instruments. The guitar was the first instrument to be popularly amplified and used by early pioneers T-Bone Walker in the late 1930 ...
and
rock music Rock music is a broad genre of popular music that originated as " rock and roll" in the United States in the late 1940s and early 1950s, developing into a range of different styles in the mid-1960s and later, particularly in the United States an ...
;
dynamic Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' "power") or dynamic may refer to: Physics and engineering * Dynamics (mechanics) ** Aerodynamics, the study of the motion of air ** Analytical dyna ...
effects such as
volume pedal An expression pedal is an important control found on many musical instruments including organs, electronic keyboards, and pedal steel guitar. The musician uses the pedal to control different aspects of the sound, commonly volume. Separate expres ...
s and compressors, which affect
loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...
;
filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
s such as
wah-wah pedal A wah-wah pedal, or simply wah pedal, is a type of electric guitar effects pedal that alters the tone and frequencies of the guitar signal to create a distinctive sound, mimicking the human voice saying the onomatopoeic name "wah-wah". The ped ...
s and
graphic equalizer Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer. Most hi-fi eq ...
s, which modify frequency ranges; modulation effects, such as
chorus Chorus may refer to: Music * Chorus (song) or refrain, line or lines that are repeated in music or in verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in which all verse ...
,
flanger Flanging is an audio signal processing, audio effect produced by mixing two identical audio signal, signals together, one signal delayed by a small and (usually) gradually changing period, usually smaller than 20 milliseconds. This produces a s ...
s and phasers; pitch effects such as pitch shifters; and time effects, such as
reverb Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abs ...
and
delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * ''The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and acto ...
, which create echoing sounds and emulate the sound of different spaces. Most modern effects use
solid-state electronics Solid-state electronics means semiconductor electronics: electronic equipment using semiconductor devices such as transistors, diodes and integrated circuits (ICs). The term is also used as an adjective for devices in which semiconductor electr ...
or digital signal processors. Some effects, particularly older ones such as Leslie speakers and
spring reverb A reverb effect, or reverb, is an audio effect applied to a sound signal to simulate reverberation. It may be created through physical means, such as echo chambers, or electronically through audio signal processing. Echo chambers The first re ...
s, use mechanical components or
vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...
s. Effects are often used as
stompboxes An effects unit or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing. Common effects include distortion/overdrive, often used with electric guitar in ele ...
, typically placed on the floor and controlled with footswitches. They may also be built into
guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
s, instruments (such as the
Hammond B-3 The Hammond organ is an electric organ invented by Laurens Hammond and John M. Hanert and first manufactured in 1935. Multiple models have been produced, most of which use sliding drawbars to vary sounds. Until 1975, Hammond organs generated ...
organ), tabletop units designed for DJs and record producers, and rackmounts, and are widely used as
audio plug-in An audio plug-in, in computer software, is a plug-in that can add or enhance audio-related functionality in a computer program. Such functionality may include digital signal processing or sound synthesis. Audio plug-ins usually provide their ...
s in such common formats as VST, AAX, and AU. Musicians, audio engineers and record producers use effects units during live performances or in the studio, typically with electric guitar, bass guitar,
electronic keyboard An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument, an electronic derivative of keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs ...
or electric piano. While effects are most frequently used with electric or electronic instruments, they can be used with any audio source, such as acoustic instruments, drums, and vocals.


Terminology

An effects unit is also called an ''effect box'', ''effects device'', ''effects processor'' or simply an ''effect''. The abbreviation ''F/X'' or ''FX'' is sometimes used. A pedal-style unit may be called a ''stomp box'', ''stompbox'', ''effects pedal'' or ''pedal''. Unprocessed audio coming into an effects unit is referred to as ''dry'', while the processed audio output is referred to as ''wet''. A musician bringing many pedals to a live show or recording session often mounts the pedals on a
guitar pedalboard A guitar pedalboard is a flat board or panel that serves as a container, patch bay, and power supply for Effects unit, effects pedals for the electric guitar. Some pedalboards contain their own transformer and power cables to power multiple peda ...
, to reduce set-up and tear-down time and, for pedalboards with lids, protect the pedals during transportation. When a musician has multiple effects in a
rack mount A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is wide. The 19 inch dimension includes the edges or "ears" that protrude from each side of the equ ...
ed
road case A road case, ATA case or flight case is a shipping container specifically built to protect musical instruments, motion picture equipment, audio and lighting production equipment, properties, firearms, or other sensitive equipment when it must be ...
, this case may be called an ''effects rack'' or ''rig''. When rackmounted effects are mounted in a roadcase, this also speeds up a musician's set-up and tear-down time, because all of the effects can be connected together inside the rack case.


Form factors

Effects units are available in a variety of form factors. Stompboxes are used in both live performance and studio recording. Rackmount devices saw a heavy usage during the later 20th century, due to their superior processing power and desirable tones as compared to pedal-style units. However, by the 21st century, with the advent of digital plugins and more powerful stompboxes for live usage, the use of rack-mounted effect units has declined.Clement, V (2007)
''How to Succeed As a Female Guitarist''
Alfred Music. p. 30–31.
An effects unit can consist of
analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...
or
digital electronics Digital electronics is a field of electronics involving the study of digital signals and the engineering of devices that use or produce them. This is in contrast to analog electronics and analog signals. Digital electronic circuits are usual ...
or a combination of the two. During a live performance, the effect is plugged into the electrical ''signal'' path of the instrument. In the studio, an instrument or another sound source — possibly an auxiliary output of a mixer or a
DAW Daw or DAW may refer to: People and language * Daw (given name) * Daw (surname) * Daw, an honorific used in Burmese name#Honorifics, Burmese names * Dâw people, an indigenous people of Brazil * Dâw language, a language of Brazil * Davaoeño lang ...
— is patched into the effect. Whatever the form factor, effects units are part of a studio or musician's
outboard gear Musical outboard equipment or outboard gear is used to process or alter a sound signal separately from functionality provided within a mixing console or a digital audio workstation. Outboard effects units can be used either during a live performanc ...
.


Stompboxes

Stompboxes are small plastic or metal chassis which usually lie on the floor or in a pedalboard to be operated by the user's feet. Pedals are often rectangle-shaped, but there are a range of other shapes (e.g., the circular
Fuzz Face The Fuzz Face is an effects pedal for electric guitar, used also by some electric bass players. It is designed to produce a distorted sound referred to as "fuzz", originally achieved through accident such as broken electrical components or damaged ...
). Typical simple stompboxes have a single footswitch, one to three
potentiometers A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. The measuring instrum ...
for controlling the effect, and a single LED that indicates if the effect is on. A typical distortion or overdrive pedal's three potentiometers, for example, control the level or intensity of the distortion effect, the tone of the effected signal and the output level of the effected signal. Depending on the type of pedal, the potentiometers may control different parameters of the effect. For a
chorus effect Chorus (or chorusing, choruser or chorused effect) is an audio effect that occurs when individual sounds with approximately the same time, and very similar pitches, converge. While similar sounds coming from multiple sources can occur naturally, ...
, for example, the knobs may control the depth and speed of the effect. Complex stompboxes may have multiple footswitches, many knobs, additional switches or buttons that are operated with the fingers, and an alphanumeric LED display that indicates the status of the effect with short acronyms (e.g., DIST for "distortion"). An ''effects chain'' or ''signal chain'' is formed by connecting two or more stompboxes. Effect chains are typically created between the guitar and the amp or between the
preamplifier A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier a ...
and the power amp. When a pedal is off or inactive, the electric audio signal coming into the pedal diverts onto a ''bypass'', an unaltered ''dry'' signal that continues on to other effects down the chain. In this way, a musician can combine effects within a chain in a variety of ways without having to reconnect boxes during a performance. A ''controller'' or ''effects management system'' lets the musician create multiple effect chains, so they can select one or several chains by tapping a single switch. The switches are usually organized in a row or a simple grid. It is common to put
compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...
, wah and overdrive pedals at the start of the chain; modulation (
chorus Chorus may refer to: Music * Chorus (song) or refrain, line or lines that are repeated in music or in verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in which all verse ...
,
flanger Flanging is an audio signal processing, audio effect produced by mixing two identical audio signal, signals together, one signal delayed by a small and (usually) gradually changing period, usually smaller than 20 milliseconds. This produces a s ...
, phase shifter) in the middle; and time-based units (
delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * ''The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and acto ...
/echo,
reverb Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abs ...
at the end. When using many effects, unwanted noise and hum can be introduced into the sound. Some performers use a noise gate pedal at the end of a chain to reduce unwanted noise and hum introduced by overdrive units or vintage gear.


Rackmounts

Rackmount effects units are typically built in a thin metal chassis with ''rack ears'' designed to be screw-mounted into the rack rails of a
19-inch rack A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is wide. The 19 inch dimension includes the edges or "ears" that protrude from each side of the equ ...
that is standard to the
music technology Music technology is the study or the use of any device, mechanism, machine or tool by a musician or composer to make or perform music; to compose, notate, playback or record songs or pieces; or to analyze or edit music. History The earli ...
industry. Rackmount effects have a standardized 19-inch width, and height of 1 or more rack unit(s). Devices that are less than 19 inches wide can sometimes be made rackmount-compatible via special rackmount adapters. A rackmount effects unit may contain electronic circuitry identical to a stompbox's, although its circuits are typically more complex. Unlike stompboxes, rackmounts usually have several different types of effects. Rackmount effects units are controlled by knobs, switches or buttons on their front panel, and often remote-controllable by a
MIDI MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
digital control interface or pedal-style ''foot controller''. Rackmount effects units are most commonly used in recording studios and front of house
live sound mixing Live sound mixing is the blending of multiple sound sources by an audio engineer using a mixing console or software. Sounds that are mixed include those from instruments and voices which are picked up by microphones (for drum kit, lead vocals an ...
situations. Musicians may use them in place of stompboxes, as use of a rack can offer space for conveniently mounting additional rackmount equipment or accessories. Rackmounted effects units are typically mounted in a rack, which may be housed within a
road case A road case, ATA case or flight case is a shipping container specifically built to protect musical instruments, motion picture equipment, audio and lighting production equipment, properties, firearms, or other sensitive equipment when it must be ...
, a durable case with removable access panels that protect the equipment within during transportation. Because of this, rackmount effect units are not always designed with durable protective features such as corner protectors which are used on stompboxes and amps that are designed to be transported as standalone units.


Multi-effects and tabletop units

A multi-effects (MFX) device is a single electronics effects pedal or rackmount device that contains many different electronic effects. multi-effects devices allow users to ''preset'' combinations of different effects, allowing musicians quick on-stage access to different effects combinations. Multi-effects units typically have a range of distortion, chorus, flanger, phaser, delay, looper and reverb effects. Pedal-style multi-effects range from fairly inexpensive stompboxes that contain two pedals and a few knobs to control the effects to large, expensive floor units with many pedals and knobs. Rack-mounted multi-effects units may be mounted in the same rack as preamplifiers and power amplifiers. A tabletop unit is a type of multi-effects device that sits on a desk and is controlled manually. One such example is the Pod guitar amplifier modeler. Digital effects designed for DJs are often sold in tabletop models, so that the units can be placed alongside a
DJ mixer A DJ mixer is a type of audio mixing console used by disc jockeys (DJs) to control and manipulate multiple audio signals. Some DJs use the mixer to make seamless transitions from one song to another when they are playing records at a dance clu ...
, turntables and
scratching Scratching, sometimes referred to as scrubbing, is a DJ and turntablist technique of moving a vinyl record back and forth on a turntable to produce percussive or rhythmic sounds. A crossfader on a DJ mixer may be used to fade between two record ...
gear.


Built-in units

Effects are often incorporated into
instrument amplifier An instrument amplifier is an electronic device that converts the often barely audible or purely electronic signal of a musical instrument into a larger electronic signal to feed to a loudspeaker. An instrument amplifier is used with musical ins ...
s and even some types of instruments. Electric
guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
s typically have built-in
reverb Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abs ...
, chorus and
distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...
, while acoustic guitar and
keyboard amplifier A keyboard amplifier is a powered electronic amplifier and loudspeaker in a wooden speaker cabinet used for amplification of electronic keyboard instruments. Keyboard amplifiers are distinct from other types of amplification systems such as ...
s tend to only have built-in reverb. Some acoustic instrument amplifiers have reverb, chorus, compression and equalization (bass and treble) effects. Vintage guitar amps typically have tremolo and
vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
effects, and sometimes reverb. The Fender Bandmaster Reverb amp, for example, had built-in reverb and vibrato. Built-in effects may offer the user less control than standalone pedals or rackmounted units. For example, on some lower- to mid-priced
bass amplifier A bass amplifier (also abbreviated to bass amp) is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audien ...
s, the only control on the audio compression effect is a button or switch to turn it on or off, or a single knob. In contrast, a pedal or rackmounted unit would typically provide ratio, threshold and attack controls or other options to allow the user additional control over the compression. Some guitar amplifiers have built-in multi-effects units or digital
amplifier modeling Amplifier modeling (also known as amp modeling or amp emulation) is the process of emulating a physical amplifier such as a guitar amplifier. Amplifier modeling often seeks to recreate the sound of one or more specific models of vacuum tube ampl ...
effects. Bass amplifiers are less likely to have built-in effects, although some may have a compressor/
limiter In electronics, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while attenuating (lowering) the peaks of stronger signals that exceed this threshold. Limiting is a type of dynamic range comp ...
or
fuzz bass Fuzz bass is a style of playing the electric bass or modifying its signal that produces a buzzy, distorted, overdriven sound, as the name implies. Overdriving a bass signal significantly changes the timbre, adds higher overtones (harmonics) ...
effect. Instruments with built-in effects include Hammond organs,
electronic organ An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since developed ...
s,
electronic piano An electronic piano is a keyboard instrument designed to simulate the timbre of a piano (and sometimes a harpsichord or an organ) using analog circuitry. "Electronic Piano" was also the trade name used for Wurlitzer's popular line of electric ...
s and digital synthesizers. Built-in effects for keyboards typically include reverb, chorus and, for Hammond organ, vibrato. Many
clonewheel organ A clonewheel organ is an electronic musical instrument that emulates (or " clones") the sound of the electromechanical tonewheel-based organs formerly manufactured by Hammond from the 1930s to the 1970s. Clonewheel organs generate sounds using so ...
s include an overdrive effect. Occasionally, acoustic-electric and electric guitars will have built-in effects, such as a preamp or equalizer.


History


Studio effects and early stand-alone units

The earliest sound effects were strictly used in studio productions. Microphones placed in
echo chamber Echo chamber of the Dresden University of Technology Hamilton Mausoleum has a long-lasting unplanned echo An echo chamber is a hollow enclosure used to produce reverberation, usually for recording purposes. For example, the producers of ...
s with specially designed acoustic properties simulated the sound of live performances in different environments. In the mid to late 1940s, recording engineers and experimental musicians such as Les Paul began manipulating reel-to-reel recording tape to create echo effects and unusual, futuristic sounds. In 1948,
DeArmond Rowe Industries was a manufacturer of guitar pickups and other music-related devices, as well as electrical components utilized in the aerospace industry into the 1980s. Owner Horace "Bud" Rowe established a working relationship with budding el ...
released the Trem-Trol, the first commercially available stand-alone effects unit. This device produced a tremolo by passing an instrument's electrical signal through a water-based electrolytic fluid. Most stand-alone effects of the 1950s and early 1960s such as the Gibson GA-VI vibrato unit and the Fender reverb box, were expensive and impractical, requiring bulky
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
s and high
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...
s. The original stand-alone units were not especially in-demand as many effects came built into amplifiers. The first popular stand-alone was the 1958
Watkins Copicat The Watkins Copicat is an audio effects unit that produces delay and reverb effects. One of the first commercially available tape delay units, the original Copicat model was produced by Watkins Electric Music beginning in 1958. The Copicat became ...
, a relatively portable tape echo effect made famous by the British band,
The Shadows The Shadows (originally known as the Drifters) were an English instrumental rock group, who dominated the British popular music charts in the late 1950s and early 1960s, in the pre- Beatles era. They served as the backing band for Cliff Richard ...
.


Amplifiers

Effects built into tube-powered guitar amplifiers were the first effects that musicians used regularly outside the studio. From the late 1940s onward, the
Gibson Gibson may refer to: People * Gibson (surname) Businesses * Gibson Brands, Inc., an American manufacturer of guitars, other musical instruments, and audio equipment * Gibson Technology, and English automotive and motorsport company based * Gi ...
began including
vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
circuits in combo amplifiers that incorporated one or more speakers with the amp. The 1950 Ray Butts EchoSonic amp was the first to feature a tape echo, which quickly became popular with guitarists such as
Chet Atkins Chester Burton Atkins (June 20, 1924 – June 30, 2001), known as "Mr. Guitar" and "The Country Gentleman", was an American musician who, along with Owen Bradley and Bob Ferguson, helped create the Nashville sound, the country music ...
, Carl Perkins,
Scotty Moore Winfield Scott Moore III (December 27, 1931 – June 28, 2016) was an American guitarist who formed The Blue Moon Boys in 1954, Elvis Presley's backing band. He was studio and touring guitarist for Presley between 1954 and 1968. Rock critic ...
,
Luther Perkins Luther Monroe Perkins (January 8, 1928 – August 5, 1968) was an American country music guitarist and a member of the Tennessee Three, the backup band for singer Johnny Cash. Perkins was an iconic figure in what would become known as rockabilly ...
, and Roy Orbison. Both Premier and Gibson built amplifiers with
spring reverb A reverb effect, or reverb, is an audio effect applied to a sound signal to simulate reverberation. It may be created through physical means, such as echo chambers, or electronically through audio signal processing. Echo chambers The first re ...
. Fender began manufacturing the tremolo amps Tremolux in 1955 and Vibrolux in 1956.
Distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...
was not an effect originally intended by amplifier manufacturers, but could often easily be achieved by "overdriving" the power supply in early
tube amplifier A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by sol ...
s. In the 1950s, guitarists began deliberately increasing
gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...
beyond its intended levels to achieve "warm" distorted sounds. Among the first musicians to experiment with distortion were Willie Johnson of
Howlin' Wolf Chester Arthur Burnett (June 10, 1910January 10, 1976), better known by his stage name Howlin' Wolf, was an American blues singer and guitarist. He is regarded as one of the most influential blues musicians of all time. Over a four-decade care ...
,
Goree Carter Goree Chester Carter or Christer Carter (December 31, 1930 – December 29, 1990), was an American singer, guitarist, drummer, and songwriter. He was also credited with the stage names Little T-Bone, Rocky Thompson and Gory Carter, and record ...
, Robert Palmer, "Church of the Sonic Guitar", pp. 13–38 in Anthony DeCurtis, ''Present Tense'',
Duke University Press Duke University Press is an academic publisher and university press affiliated with Duke University. It was founded in 1921 by William T. Laprade as The Trinity College Press. (Duke University was initially called Trinity College). In 1926 D ...
, 1992, p. 19. .
Joe Hill Louis Joe Hill Louis (September 23, 1921 – August 5, 1957), born Lester Hill, was an American singer, guitarist, harmonica player and one-man band. He was one of a small number of one-man blues bands (along with fellow Memphis bluesman Doctor Ross) ...
,
Ike Turner Izear Luster "Ike" Turner Jr. (November 5, 1931 – December 12, 2007) was an American musician, bandleader, songwriter, record producer, and talent scout. An early pioneer of 1950s rock and roll, he is best known for his work in the 1960s and ...
,
Guitar Slim Eddie Jones (December 10, 1926 – February 7, 1959), better known as Guitar Slim, was an American guitarist in the 1940s and 1950s, best known for the million-selling song " The Things That I Used to Do", for Specialty Records. It is listed in t ...
, and
Chuck Berry Charles Edward Anderson Berry (October 18, 1926 – March 18, 2017) was an American singer, songwriter and guitarist who pioneered rock and roll. Nicknamed the " Father of Rock and Roll", he refined and developed rhythm and blues into th ...
. In 1954,
Pat Hare Auburn "Pat" Hare was a Memphis electric blues guitarist and singer. His heavily distortion (music), distorted, power chord–driven electric guitar performances in the early 1950s is considered an important precursor of heavy metal music.Robert P ...
produced heavily distorted
power chord A power chord (also fifth chord) is a colloquial name for a chord in guitar music, especially electric guitar, that consists of the root note and the fifth, as well as possibly octaves of those notes. Power chords are commonly played on ...
s for several recordings (including
James Cotton James Henry Cotton (July 1, 1935 – March 16, 2017) was an American blues harmonica player, singer and songwriter, who performed and recorded with many fellow blues artists and with his own band. He also played drums early in his career. ...
's Cotton Crop Blues"), creating "a grittier, nastier, more ferocious electric guitar sound," Robert Palmer, "Church of the Sonic Guitar", pp. 13–38 in Anthony DeCurtis, ''Present Tense'',
Duke University Press Duke University Press is an academic publisher and university press affiliated with Duke University. It was founded in 1921 by William T. Laprade as The Trinity College Press. (Duke University was initially called Trinity College). In 1926 D ...
, 1992, pp. 24–27. .
accomplished by turning the volume knob on his amplifier "all the way to the right until the speaker was screaming." Link Wray's 1958 recording " Rumble" inspired young musicians such as
Pete Townshend Peter Dennis Blandford Townshend (; born 19 May 1945) is an English musician. He is co-founder, leader, guitarist, second lead vocalist and principal songwriter of the Who, one of the most influential rock bands of the 1960s and 1970s. Townsh ...
of
The Who The Who are an English rock band formed in London in 1964. Their classic lineup consisted of lead singer Roger Daltrey, guitarist and singer Pete Townshend, bass guitarist and singer John Entwistle, and drummer Keith Moon. They are considered ...
, Jimmy Page of
Led Zeppelin Led Zeppelin were an English rock band formed in London in 1968. The group comprised vocalist Robert Plant, guitarist Jimmy Page, bassist/keyboardist John Paul Jones, and drummer John Bonham. With a heavy, guitar-driven sound, they are ci ...
, Jeff Beck,
Dave Davies David Russell Gordon Davies (born 3 February 1947) is an English guitarist, singer and songwriter. He was the lead guitarist and backing vocalist for the English rock band the Kinks, which also featured his elder brother Ray Davies. He was in ...
of
The Kinks The Kinks were an English rock band formed in Muswell Hill, north London, in 1963 by brothers Ray and Dave Davies. They are regarded as one of the most influential rock bands of the 1960s. The band emerged during the height of British rhyt ...
, and
Neil Young Neil Percival Young (born November 12, 1945) is a Canadian-American singer and songwriter. After embarking on a music career in Winnipeg in the 1960s, Young moved to Los Angeles, joining Buffalo Springfield with Stephen Stills, Richie Fur ...
to explore distortion by various means. In 1966, the British company Marshall Amplification began producing the Marshall 1963, a guitar amplifier capable of producing the distorted "crunch" that rock musicians were starting to seek.


Stompboxes

The electronic
transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
finally made it possible to cram the aural creativity of the recording studio into small, highly portable stompbox units. Transistors replaced
vacuum tubes A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as a ...
, allowing for much more compact formats and greater stability. The first transistorized guitar effect was the 1962 Maestro Fuzz Tone pedal, which became a sensation after its use in the 1965 Rolling Stones hit " (I Can't Get No) Satisfaction". Warwick Electronics manufactured the first
wah-wah pedal A wah-wah pedal, or simply wah pedal, is a type of electric guitar effects pedal that alters the tone and frequencies of the guitar signal to create a distinctive sound, mimicking the human voice saying the onomatopoeic name "wah-wah". The ped ...
, The Clyde McCoy, in 1967 and that same year Roger Mayer developed the first
octave effect Octave effect boxes are a type of special effects unit which mix the input signal with a synthesised signal whose musical tone is an octave lower or higher than the original. The synthesised octave signal is derived from the original input signa ...
, which Jimi Hendrix named "Octavio". Upon first hearing the Octavia, Hendrix allegedly rushed back to the studio and immediately used it to record the guitar solos on " Purple Haze" and "
Fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames a ...
". In 1968,
Univox Univox was a musical instrument brand of Unicord Corporation from the early 1960s, when they purchased the Amplifier Corporation of America of Westbury, New York and began to market a line of guitar amplifiers. Univox also distributed guitars by ...
began marketing Shin-ei's
Uni-Vibe The Uni-Vibe, also marketed as the Jax Vibra-Chorus,Harry Shapiro, Michael Heatley, Roger Mayer''Jimi Hendrix Gear'', page 120 Voyageur Press is a footpedal-operated phaser or phase shifter for creating chorus and vibrato simulations for elec ...
pedal, an effect designed by noted audio engineer Fumio Mieda that mimicked the odd
phase shift In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it ...
and
chorus Chorus may refer to: Music * Chorus (song) or refrain, line or lines that are repeated in music or in verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in which all verse ...
effects of the Leslie rotating speakers used in Hammond organs. The pedals soon became favorite effects of guitarists Jimi Hendrix and
Robin Trower Robin Leonard Trower (born 9 March 1945) is an English rock guitarist who achieved success with Procol Harum throughout 1967–1971, and then again as the bandleader of his own power trio known as the Robin Trower Band. Biography Robin Trowe ...
. In 1976, Roland subsidiary Boss Corporation released the CE-1 Chorus Ensemble, the first
chorus pedal Chorus (or chorusing, choruser or chorused effect) is an audio effect that occurs when individual sounds with approximately the same time, and very similar pitches, converge. While similar sounds coming from multiple sources can occur naturally, ...
, created by taking a chorus circuit from an
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
and putting it into a stompbox.Tribute: Ikutaro Kakehashi and Roland's Impact on Music
Reverb.com Reverb.com is an online marketplace for new, used, and vintage music gear. It was founded in 2013 by David Kalt, shortly after he purchased the musical instrument store Chicago Music Exchange and became frustrated with then-available options f ...
By the mid-1970s a variety of solid-state effects pedals including
flanger Flanging is an audio signal processing, audio effect produced by mixing two identical audio signal, signals together, one signal delayed by a small and (usually) gradually changing period, usually smaller than 20 milliseconds. This produces a s ...
s, chorus pedals,
ring modulator In electronics, ring modulation is a signal processing function, an implementation of frequency mixing, in which two signals are combined to yield an output signal. One signal, called the carrier, is typically a sine wave or another simple ...
s and phase shifters were available. In the 1980s, digital
rackmount A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is wide. The 19 inch dimension includes the edges or "ears" that protrude from each side of the equ ...
units began replacing stompboxes as the effects format of choice. Often musicians would record "dry", unaltered tracks in the studio and effects would be added in post-production. The success of
Nirvana ( , , ; sa, निर्वाण} ''nirvāṇa'' ; Pali: ''nibbāna''; Prakrit: ''ṇivvāṇa''; literally, "blown out", as in an oil lampRichard Gombrich, ''Theravada Buddhism: A Social History from Ancient Benāres to Modern Colombo.' ...
's 1991 album ''
Nevermind ''Nevermind'' is the second studio album by the American rock band Nirvana, released on September 24, 1991, by DGC Records. It was Nirvana's first release on a major label and the first to feature drummer Dave Grohl. Produced by Butch Vig, '' ...
'' helped to re-ignite interest in stompboxes. Some grunge guitarists would chain several fuzz pedals together and plug them into a
tube amplifier A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by sol ...
. Throughout the 1990s, musicians committed to a "
lo-fi Lo-fi (also typeset as lofi or low-fi; short for low fidelity) is a music or production quality in which elements usually regarded as imperfections in the context of a recording or performance are present, sometimes as a deliberate choice. The ...
" aesthetic such as
J Mascis Joseph Donald Mascis Jr. ( ; born December 10, 1965), better known as J Mascis, is an American musician who is the singer, guitarist and main songwriter for the alternative rock band Dinosaur Jr. He has also released several albums as a solo art ...
of
Dinosaur Jr. Dinosaur Jr. is an American rock band formed in Amherst, Massachusetts, in 1984, originally simply called Dinosaur until legal issues forced a change in name. The band was founded by J Mascis (guitar, vocals, primary songwriter), Lou Barlo ...
,
Stephen Malkmus Stephen Joseph Malkmus (born May 30, 1966) is an American musician best known as the primary songwriter, lead singer and guitarist of the indie rock band Pavement. He currently performs with Stephen Malkmus and the Jicks and as a solo artist. ...
of Pavement and
Robert Pollard Robert Ellsworth Pollard Jr. (born October 31, 1957) is an American singer and songwriter who is the leader and creative force behind indie rock group Guided by Voices. In addition to his work with Guided by Voices, he continues to have a prol ...
of Guided by Voices continued to use
analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...
effects pedals. Effects and effects units—stompboxes in particular—have been celebrated by pop and rock musicians in album titles, songs and band names. The
Big Muff The Big Muff Pi (π), often known simply as the Big Muff, is a fuzzbox produced in New York City by the Electro-Harmonix company, along with their Russian sister company Sovtek, primarily for use with the electric guitar. It is used by bassist ...
, a
fuzzbox Distortion and overdrive are forms of audio signal processing used to alter the sound of amplified electric musical instruments, usually by increasing their gain, producing a "fuzzy", "growling", or "gritty" tone. Distortion is most commonly ...
manufactured by
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
, is commemorated by the Depeche Mode song "
Big Muff The Big Muff Pi (π), often known simply as the Big Muff, is a fuzzbox produced in New York City by the Electro-Harmonix company, along with their Russian sister company Sovtek, primarily for use with the electric guitar. It is used by bassist ...
" and the Mudhoney EP ''
Superfuzz Bigmuff ''Superfuzz Bigmuff'' is the debut EP and first major release by the Seattle grunge band Mudhoney. It was released on October 20, 1988 through record label Sub Pop. The album was later re-released in 1990 in the form of ''Superfuzz Bigmuff Plus Ea ...
''. Nine Inch Nails, Pink Floyd, George Harrison,
They Might Be Giants They Might Be Giants (often abbreviated as TMBG) is an American alternative rock band formed in 1982 by John Flansburgh and John Linnell. During TMBG's early years, Flansburgh and Linnell frequently performed as a duo, often accompanied by a ...
and
Joy Division Joy Division were an English rock band formed in Salford in 1976. The group consisted of vocalist Ian Curtis, guitarist/keyboardist Bernard Sumner, bassist Peter Hook and drummer Stephen Morris. Sumner and Hook formed the band after atte ...
are among the many musicians who have referenced effects units in their music.


Types


Distortion

Distortion, overdrive, and fuzz effects units add a "warm", "gritty", or "fuzzy" character to an audio signal by re-shaping or "
clipping Clipping may refer to: Words * Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement" * Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel * Clipping (publications) ...
" it, which distorts the shape of its
wave form In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (r ...
by flattening its peaks, creating "warm" sounds by adding
harmonics A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', ...
or "gritty" sounds by adding
inharmonic In music, inharmonicity is the degree to which the frequencies of overtones (also known as partials or partial tones) depart from whole multiples of the fundamental frequency ( harmonic series). Acoustically, a note perceived to have a singl ...
overtones. Distortion effects are sometimes called "
gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...
" effects, as distorted guitar sounds were first achieved by increasing the electric power supply, e.g. gain, to
tube amplifier A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by sol ...
s.Aikin, Jim (2004)
''Power Tools for Synthesizer Programming''
Hal Leonard. p. 171.
While distortion effects units produce perfectly flattened peaks or "hard" clipping, overdrive effects units produce "soft" tube-like distortion by compressing the sine wave without completely flattening it. Much like guitar tube amplifiers, overdrive effects units are capable of producing "clean" sounds at quieter volumes and distorted "warm" sounds at louder volumes. Notable examples of distortion and overdrive effects units include the
Boss DS-1 The Boss DS-1 is a distortion pedal for guitar, manufactured by the Roland Corporation under the brand name Boss since 1978. The first distortion effects unit made by Boss, it has become a classic effect, used by many notable guitar players. B ...
Distortion,
Ibanez Tube Screamer The Ibanez Tube Screamer (TS808/TS9) is a guitar overdrive pedal, made by Ibanez. The pedal has a characteristic mid-boosted tone popular with blues, rock and metal players. The Tube Screamer has been used by many guitarists to create their signa ...
,
Marshall ShredMaster The Marshall ShredMaster (also known as the Shred Master) is a discontinued distortion pedal which was manufactured by Marshall Amps. It was the high-gain pedal of a triad, also including the Marshall DriveMaster and the Marshall BluesBreaker. ...
, MXR Distortion +, and
Pro Co RAT The Pro Co "The RAT" is a distortion pedal produced by Pro Co Sound. The original RAT was developed in the basement of Pro Co's Kalamazoo, Michigan facility in 1978. Numerous variations of the original RAT pedal are still being produced today. The ...
. A fuzz pedal, or fuzzbox, is a type of overdrive effects unit that clips a sound-wave until it is nearly a
squarewave A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum. In an ideal square wave, the transitions b ...
, resulting in a heavily distorted or "fuzzy" sound. Fuzzboxes may contain
frequency multiplier In electronics, a frequency multiplier is an electronic circuit that generates an output signal and that output frequency is a harmonic (multiple) of its input frequency. Frequency multipliers consist of a nonlinear circuit that distorts the in ...
circuitry An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...
to achieve a harsh
timbre In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musica ...
by adding complex
harmonics A harmonic is a wave with a frequency that is a positive integer multiple of the '' fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', ...
.
The Rolling Stones The Rolling Stones are an English Rock music, rock band formed in London in 1962. Active for six decades, they are one of the most popular and enduring bands of the album era, rock era. In the early 1960s, the Rolling Stones pioneered the g ...
' song " (I Can't Get No) Satisfaction", with a fuzz effect featured prominently on the main electric guitar riff played by Keith Richards, greatly popularized the use of fuzz effects.
Fuzz bass Fuzz bass is a style of playing the electric bass or modifying its signal that produces a buzzy, distorted, overdriven sound, as the name implies. Overdriving a bass signal significantly changes the timbre, adds higher overtones (harmonics) ...
(also called "bass overdrive") is a style of playing the electric bass that produces a buzzy, overdriven sound via a tube or transistor amp or by using a fuzz or overdrive pedal. Notable examples of fuzz effect units include the: Arbiter Fuzz Face, Electro-Harmonix Big Muff,
Shin-ei Companion FY-2 The Shin-ei Companion FY-2 is a discontinued fuzz pedal, made by the Japanese Shin-ei effects pedal company from the late 1960s to the early 1970s. The pedal is known for its raw, distinctive, gated fuzz. FY-2 pedals are now rare. Different versio ...
,
Univox Super-Fuzz The Univox Super-Fuzz was a fuzzbox produced by the Univox company, primarily for use with the electric guitar or bass. History Origin The circuit was designed in the late 1960s by the Japanese company Honey, in the form of a multi effect call ...
, Vox Tone Bender, Z.Vex Fuzz Factory. While distortion effect units are most associated with electric and bass guitar, they are also commonly used on keyboard instruments (i.e. synthesizers,
combo Combo may refer to: Technology *Combo television unit, a television with either a VCR or a DVD player built into a single unit * Combo drive, a type of optical drive that can read CDs and DVDs *A guitar amplifier incorporating one or more loudsp ...
and tonewheel organs, electric piano), as well as drums and vocals. Distortion and overdrive effects units may either be
transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
-based or digital.


Dynamics

Also called volume and
amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
effects, dynamics effects modify the volume of an instrument. Dynamics effects were among the first effects introduced to guitarists. ''Boost/volume pedal'': A boost or "clean boost" pedal amplifies the volume of an instrument by increasing the
amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
of its audio signal. These units are generally used for "boosting" volume during solos and preventing signal loss in long " effects chains". A guitarist switching from rhythm guitar to lead guitar for a guitar solo may use a boost to increase the volume of their solo. Treadle-based volume pedals are used by electric instrument players (guitar, bass, keyboards) to adjust the volume of their instrument with one foot while their hands are being used to play their instrument. Treadle-style volume pedals are often also used to create swelling effects by removing the attack of a note or chord, as popularised by pedal steel guitar players. This enables electric guitar and pedal steel players to imitate the soft swelling sound that an orchestra string section can produce, in which a note or chord starts very softly and then grows in volume. Treadle-based volume pedals do not usually have batteries or require external power. Volume effects:
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
LPB-1, Fender Volume Pedal, MXR Micro Amp,
Ernie Ball Ernie Ball (born Roland Sherwood Ball; August 30, 1930 – September 9, 2004) was an American entrepreneur and musician who developed guitar-related products. Ball began as a club and local television musician and entrepreneur, building an inte ...
Volume Pedal. '' Compressor'': Compressors make loud sounds quieter and quiet sounds louder by decreasing or "compressing" the
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of Signal (electrical engineering), signals, like sound and light. It is measured ...
of an audio signal. A compressor is often used to stabilize volume and smooth a note's "attack" by dampening its onset and amplifying its sustain. A compressor can also function as a
limiter In electronics, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while attenuating (lowering) the peaks of stronger signals that exceed this threshold. Limiting is a type of dynamic range comp ...
with extreme settings of its controls.Hunter, D (2004)
''Guitar Effects Pedals: The Practical Handbook''
Hal Leonard. p. 23.
Compressor effects: Keeley Compressor, MXR Dyna Comp, Boss CS-3 Compression Sustainer. ''
Noise gate A noise gate or gate is an electronic device or software that is used to control the volume of an audio signal. Comparable to a compressor, which attenuates signals ''above'' a threshold, such as loud attacks from the start of musical notes, no ...
'': Noise gates
attenuate In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at vari ...
hum, hiss, and static in the signal by greatly diminishing the volume when the signal falls below a set threshold. Noise gates are often used by electric guitarist who play with vintage amps, which can have unwanted hum in the tone, and by guitarists from heavy metal who use high
distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...
levels, which add noise to the signal even when no notes are being played. Noise gates mute the signal when it falls below a certain threshold. This means that during bars of rest for the guitarist in a song, the hum or noise from the amp or distortion pedal will not be heard by the audience. Noise gates are expanders—meaning that, unlike compressors, they increase the
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of Signal (electrical engineering), signals, like sound and light. It is measured ...
of an audio signal to make quiet sounds even quieter. If used with extreme settings and combined with reverb, they can create unusual sounds, such as the gated drum effect used in 1980s pop songs, a style popularized by the Phil Collins song ''
In the Air Tonight "In the Air Tonight" is the debut solo single by English drummer and singer-songwriter Phil Collins. It was released as the lead single from Collins's debut solo album, ''Face Value'', in January 1981. Collins co-produced "In the Air Tonight" w ...
''. Noise gate effects: Boss NS-2 Noise Suppressor.


Filter

Filter effects alter the
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
content of an audio signal that passes through them by either boosting or weakening specific frequencies or frequency regions. '' Equalizer'': An equalizer is a set of
linear filter Linear filters process time-varying input signals to produce output signals, subject to the constraint of linearity. In most cases these linear filters are also time invariant (or shift invariant) in which case they can be analyzed exactly using ...
s that strengthen ("boost") or weaken ("cut") specific
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
regions. While basic home stereos often have equalizers for two bands, to adjust bass and treble, professional
graphic equalizer Equalization, or simply EQ, in sound recording and reproduction is the process of adjusting the volume of different frequency bands within an audio signal. The circuit or equipment used to achieve this is called an equalizer. Most hi-fi eq ...
s offer much more targeted control over the audio frequency spectrum.
Audio engineers An audio engineer (also known as a sound engineer or recording engineer) helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction, ...
use highly sophisticated equalizers to eliminate unwanted sounds, make an instrument or voice more prominent, and enhance particular aspects of an instrument's tone. Equalizer effects: Boss GE-7 Equalizer, MXR 10-band EQ Pedal. ''
Talk box A talk box (also spelled talkbox and talk-box) is an effects unit that allows musicians to modify the sound of a musical instrument by shaping the frequency content of the sound and to apply speech sounds (in the same way as singing) onto the sou ...
'': A talk box directs the sound from an electric guitar or synthesizer into the mouth of a performer using a tube, allowing the sound to be shaped into
vowel A vowel is a syllabic speech sound pronounced without any stricture in the vocal tract. Vowels are one of the two principal classes of speech sounds, the other being the consonant. Vowels vary in quality, in loudness and also in quantity (leng ...
s and
consonant In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are and pronounced with the lips; and pronounced with the front of the tongue; and pronounced wi ...
s with movements of the mouth. The modified sound is then picked up by a microphone. In this way the guitarist is able create the effect that the guitar "licks" are "talking". Some famous uses of the talkbox include Bon Jovi's "
Livin' on a Prayer "Livin' on a Prayer" is a song by the American rock band Bon Jovi, and is the band's second chart-topping single from their third album '' Slippery When Wet''. Written by Jon Bon Jovi, Richie Sambora and Desmond Child, the single, released in ...
", Stevie Wonder's " Black Man", Mötley Crüe's "
Kickstart My Heart "Kickstart My Heart" is a song by American heavy metal band Mötley Crüe, originally released on their 1989 album, '' Dr. Feelgood''. Released as the album's second single in 1989, "Kickstart My Heart" reached #27 on the ''Billboard'' Hot 100 ...
",
Joe Walsh Joseph Fidler Walsh (born November 20, 1947) is an American guitarist, singer, and songwriter. In a career spanning over five decades, he has been a member of three successful rock bands: the James Gang, Eagles, and Ringo Starr & His All-Starr ...
's "
Rocky Mountain Way "Rocky Mountain Way" is a 1973 song by rock guitarist Joe Walsh and his band Barnstorm, with writing credits given to all four band members: Walsh, Rocke Grace, Kenny Passarelli, and Joe Vitale. The song was originally released on the album '' ...
",
Alice in Chains Alice in Chains (often abbreviated as AIC) is an American rock band from Seattle, Washington, formed in 1987 by guitarist and vocalist Jerry Cantrell and drummer Sean Kinney, who later recruited bassist Mike Starr and lead vocalist Layne ...
's "
Man in the box "Man in the Box" is a song by the American rock band Alice in Chains. It was released as a single in January 1991 after being featured on the group's debut studio album, ''Facelift'' (1990). It peaked at No. 18 on ''Billboards Mainstream Rock ...
" and Peter Frampton's " Show Me the Way". Talk boxes: Dunlop HT1 Heil Talk Box, Rocktron Banshee. '' Wah-wah'': A wah-wah pedal creates vowel-like sounds by altering the
frequency spectrum The power spectrum S_(f) of a time series x(t) describes the distribution of power into frequency components composing that signal. According to Fourier analysis, any physical signal can be decomposed into a number of discrete frequencies, ...
produced by an instrument—i.e., how loud it is at each separate
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
—in what is known as a "
spectral glide A spectral glide is a music-composition concept, consisting of a "modification of the vowel quality of a tone" (Erickson 1975, p. 72). Since the vowel quality of a tone is determined by the overtones, spectrum, or timbre of that tone (all th ...
" or "sweep". The device is operated by a foot treadle that opens and closes a
potentiometer A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat. The measuring instrum ...
. Wah-wah pedals are often used by funk and rock guitarists.Schneider, John (1985)
''The Contemporary Guitar''
University of California Press. p. 202.
Wah effects: Dunlop Cry Baby, Morley Power Wah
Vox V846 Wah
''
Auto-wah Auto-wah (also known as a "Q-wah", "T-wah", "envelope following filter", "envelope follower" or "envelope filter") is a type of wah-wah effects pedal typically used with electric guitar, bass guitar, clavinet, and electric piano etc. The distinc ...
'': A filter effect that is controlled by the volume of the input signal.''The Boss Book: The Ultimate Guide to the World's Most Popular Compact Effects for Guitar'', 2002, Hal Leonard Corporation The most common filter type used for this effect pedal is the low-pass filter, although many pedal designs include a toggle for band-pass or high-pass filters as well. Additionally, most envelope filters pedal boxes can switch between a down filter mode and an up filter. This effect is commonly used in funk, reggae and jam band music. Envelope filter effects:
Musitronics Mu-Tron III ''Musitronics'', often shortened to Mu-tron, was a manufacturer of electronic musical effects active in the 1970s. Founded by Mike Beigel and Aaron Newman, the company's products provided filtering and processing effects and were derived from s ...

Electro-Harmonix Q-Tron Plus


Modulation

''Modulation'', in general electronics, means the altering of signal strength. In audio devices, modulation is a control feature that varies the strength of some effect over time to alter tonal properties. Some modulation effects mix (" modulate") an instrument's audio signal with a signal generated by the effect called a
carrier wave In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has ...
. Other modulation effects split an instrument's audio signal in two, altering one portion of the signal and mixing it with the unaltered portion.Coulter, Doug. (2001)
''Digital Audio Processing''
Focal Press. p. 271.
''
Chorus Chorus may refer to: Music * Chorus (song) or refrain, line or lines that are repeated in music or in verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in which all verse ...
'': Chorus pedals mimic the effect
choir A choir ( ; also known as a chorale or chorus) is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform. Choirs may perform music from the classical music repertoire, which sp ...
s and string orchestras produce naturally, by having slight variations in timbre and pitch, by mixing sounds with slight differences in
timbre In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musica ...
and pitch. A chorus effect splits the instrument-to-amplifier audio signal, and adds a slight delay and
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
variations or ''
vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
'' to part of the signal while leaving the rest unaltered. A well-known usage of chorus is the lead guitar in " Come As You Are" by
Nirvana ( , , ; sa, निर्वाण} ''nirvāṇa'' ; Pali: ''nibbāna''; Prakrit: ''ṇivvāṇa''; literally, "blown out", as in an oil lampRichard Gombrich, ''Theravada Buddhism: A Social History from Ancient Benāres to Modern Colombo.' ...
. Chorus effects: Boss CE-1 Chorus Ensemble,
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
Small Clone,
TC Electronic TC Electronic (sometimes stylized as t.c. electronic) is a Danish audio equipment company that designs and imports guitar effects, bass amplification, computer audio interfaces, audio plug-in software, live sound equalisers, studio and post-pr ...
Stereo Chorus. ''
Flanger Flanging is an audio signal processing, audio effect produced by mixing two identical audio signal, signals together, one signal delayed by a small and (usually) gradually changing period, usually smaller than 20 milliseconds. This produces a s ...
'': A flanger creates a "whooshing" "jet plane" or "spaceship" sound, simulating a studio effect that was first produced by recording a track on two synchronized
tapes Tape or Tapes may refer to: Material A long, narrow, thin strip of material (see also Ribbon (disambiguation): Adhesive tapes * Adhesive tape, any of many varieties of backing materials coated with an adhesive * Athletic tape, pressure-sensiti ...
and periodically slowing one tape by pressing the edge of its reel (the "flange"). When the two tapes' audio signals are later mixed, a
comb filter In signal processing, a comb filter is a filter implemented by adding a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly space ...
effect can be heard. Flanger units add a variably delayed version of the audio signal to the original or signal, creating a comb filter or Doppler effect. Some famous uses of flanger effects include "
Walking on the Moon "Walking on the Moon" is a song by British rock band the Police, released as the second single from their second studio album, ''Reggatta de Blanc'' (1979). The song was written by the band's lead vocalist and bassist Sting. It went on to beco ...
" by
The Police The Police were an English rock band formed in London in 1977. For most of their history the line-up consisted of primary songwriter Sting (lead vocals, bass guitar), Andy Summers (guitar) and Stewart Copeland (drums, percussion). The Polic ...
, the intro to "
Ain't Talkin' 'Bout Love "Ain't Talkin' 'bout Love" is a song by American rock band Van Halen. It was released in October 1978 as the third single from their 1978 debut album, ''Van Halen''. This song is one of the few David Lee Roth-era songs that subsequent replaceme ...
" by
Van Halen Van Halen ( ) was an American rock band formed in Pasadena, California, in 1972. Credited with "restoring hard rock to the forefront of the music scene", Van Halen was known for its energetic live shows and for the virtuosity of its lead gu ...
, and "
Barracuda A barracuda, or cuda for short, is a large, predatory, ray-finned fish known for its fearsome appearance and ferocious behaviour. The barracuda is a saltwater fish of the genus ''Sphyraena'', the only genus in the family Sphyraenidae, which was ...
" by
Heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...
. Flanger effects:
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
Electric Mistress, MXR Flanger, Boss BF-3 Flanger. '' Phaser'': A phaser or "phase shifter" creates a slight rippling effect—amplifying some aspects of the tone while diminishing others—by splitting an audio signal in two and altering the
phase Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform * Phase space, a mathematic ...
of one portion. Three well-known examples of phaser are the two handed tapping part on the Van Halen instrumental "
Eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often ...
" and the keyboard parts on Billy Joel's " Just the Way You Are" and Paul Simon's "
Slip Slidin' Away "Slip Slidin' Away" is a 1977 song written and recorded by Paul Simon which appears on his compilation album '' Greatest Hits, Etc.'' It was one of two new songs to appear on the album, the other being "Stranded in a Limousine". Backing vocals ...
". Phase shift effects:
Uni-Vibe The Uni-Vibe, also marketed as the Jax Vibra-Chorus,Harry Shapiro, Michael Heatley, Roger Mayer''Jimi Hendrix Gear'', page 120 Voyageur Press is a footpedal-operated phaser or phase shifter for creating chorus and vibrato simulations for elec ...
,
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
Small Stone,
MXR Phase 90 The MXR Phase 90 is a phaser effects pedal introduced in 1972 by MXR. History The Phase 90 was the first pedal sold by MXR and helped launch the company in 1974. The original model had a simple orange enclosure with a script style MXR logo. In ...
. ''
Ring modulator In electronics, ring modulation is a signal processing function, an implementation of frequency mixing, in which two signals are combined to yield an output signal. One signal, called the carrier, is typically a sine wave or another simple ...
'': A ring modulator produces a resonant, metallic sound by mixing an instrument's audio signal with a
carrier wave In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has ...
generated by the device's internal oscillator. The original sound wave is suppressed and replaced by a "ring" of
inharmonic In music, inharmonicity is the degree to which the frequencies of overtones (also known as partials or partial tones) depart from whole multiples of the fundamental frequency ( harmonic series). Acoustically, a note perceived to have a singl ...
higher and lower pitches or "
sideband In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal. The sidebands c ...
s". A notable use of
ring modulation In electronics, ring modulation is a signal processing function, an implementation of frequency mixing, in which two signals are combined to yield an output signal. One signal, called the carrier, is typically a sine wave or another simple ...
is the guitar in the
Black Sabbath Black Sabbath were an English rock music, rock band formed in Birmingham in 1968 by guitarist Tony Iommi, drummer Bill Ward (musician), Bill Ward, bassist Geezer Butler and vocalist Ozzy Osbourne. They are often cited as pioneers of heavy met ...
song "
Paranoid Paranoia is an instinct or thought process that is believed to be heavily influenced by anxiety or fear, often to the point of delusion and irrationality. Paranoid thinking typically includes persecutory beliefs, or beliefs of conspiracy c ...
". Ring modulator effects: Moogerfooger MF-102 Ring Modulator. '' Tremolo'': A tremolo effect produces a slight, rapid variation in the volume of a note or chord. The "tremolo effect" should not be confused with the misleadingly-named ''
tremolo bar A vibrato system on a guitar is a mechanical device used to temporarily change the pitch of the strings. Instruments without a vibrato have other bridge and tailpiece systems. They add vibrato to the sound by changing the tension of the string ...
'', a device on a guitar bridge that creates a
vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
or pitch-bending effect. In
transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
ized effects, a tremolo is produced by modulating an instrument's audio signal with a sub-audible carrier wave in such a way that generates
amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...
variations in the sound wave. Tremolo effects are built-in effects in some vintage
guitar amplifiers A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
. The guitar intro in the Rolling Stones' "
Gimme Shelter "Gimme Shelter" is a song by English rock band the Rolling Stones. Released as the opening track from band's 1969 album ''Let It Bleed''. The song covers topics of war, murder, rape and fear. It features prominent guest vocals by American singe ...
" features a tremolo effect. Tremolo effects: Demeter TRM-1 Tremulator,
Fender Tremolux The Fender Tremolux was a guitar amplifier made by Fender. It was introduced in the summer of 1955 with a rated power output of 15 watts, cathode bias, two 6V6 output tubes, and a 5V4 tube rectifier. The Tremolux was the first Fender amp with a bu ...
. '' Slicer'': Combines a modulation sequence with a
noise gate A noise gate or gate is an electronic device or software that is used to control the volume of an audio signal. Comparable to a compressor, which attenuates signals ''above'' a threshold, such as loud attacks from the start of musical notes, no ...
or
envelope filter Auto-wah (also known as a "Q-wah", "T-wah", "envelope following filter", "envelope follower" or "envelope filter") is a type of wah-wah effects pedal typically used with electric guitar, bass guitar, clavinet, and electric piano etc. The disti ...
to create a percussive and rhythmic effect like a helicopter. ''
Vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
'': Vibrato effects produce slight, rapid variations in pitch, mimicking the fractional
semitone A semitone, also called a half step or a half tone, is the smallest musical interval commonly used in Western tonal music, and it is considered the most dissonant when sounded harmonically. It is defined as the interval between two adjacent no ...
variations produced naturally by
opera singer Opera is a form of theatre in which music is a fundamental component and dramatic roles are taken by singers. Such a "work" (the literal translation of the Italian word "opera") is typically a collaboration between a composer and a libretti ...
s and violinists when they are prolonging a single note. Vibrato effects often allow the performer to control the rate of the variation as well as the difference in pitch (e.g. "depth"). A vibrato with an extreme "depth" setting (e.g., half a semitone or more) will produce a dramatic, ululating sound. In
transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
ized effects, vibrato is produced by mixing an instrument's audio signal with a
carrier wave In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform (usually sinusoidal) that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has ...
in such a way that generates
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
variations in the sound wave. Guitarists often use the terms ''
vibrato Vibrato ( Italian, from past participle of " vibrare", to vibrate) is a musical effect consisting of a regular, pulsating change of pitch. It is used to add expression to vocal and instrumental music. Vibrato is typically characterised in terms ...
'' and " tremolo" misleadingly. A so-called "vibrato unit" in a guitar amplifier actually produces tremolo, while a "
tremolo arm A vibrato system on a guitar is a mechanical device used to temporarily change the pitch of the strings. Instruments without a vibrato have other bridge and tailpiece systems. They add vibrato to the sound by changing the tension of the strin ...
" or "whammy bar" on a guitar produces vibrato. Vibrato effects: Boss VB-2 Vibrato.


Pitch/frequency

Pitch/frequency effects modify pitch by altering the
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
of a sound wave or sound signal or adding new
harmonies In music, harmony is the process by which individual sounds are joined together or composed into whole units or compositions. Often, the term harmony refers to simultaneously occurring frequencies, pitches ( tones, notes), or chords. However ...
. ''
Pitch shifter Pitch shifting is a sound recording technique in which the original pitch of a sound is raised or lowered. Effects units that raise or lower pitch by a pre-designated musical interval ( transposition) are called pitch shifters. Pitch and ti ...
and harmonizer''" A pitch shifter (also called an "octaver" for effects that shift pitch by an octave) raises or lowers (e.g. " transposes") each note a performer plays by a pre-set interval. For example, a pitch shifter set to increase the pitch by a fourth will raise each note four diatonic intervals above the notes actually played. Simple, less expensive pitch shifters raise or lower the pitch by one or two octaves, while more sophisticated and expensive devices offer a range of interval alterations. A pitch shifter can be used by an electric guitarist to play notes that would normally only be available on an electric bass. As well, a bass player with a four string electric bass can use an octave pedal to obtain low notes that would normally only be obtainable with a five-string bass with a low "B" string. A harmonizer is a type of sophisticated pitch shifter that combines the altered pitch with the original pitch to create a two note harmony based on the original pitch, or even with some pedals, three note harmony. Some hamonizers are able to create chorus-like effects by adding very tiny shifts in pitch. Pitch shift effects:
DigiTech Whammy The DigiTech Whammy is a pitch shifter pedal manufactured by DigiTech. It was the first widely used effects pedal that could do foot-controlled pitch shifting effects. The pedal emulates sounds that a guitarist normally makes using the vibrato ...
,
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
POG.


Time-based

Time-based effects delay the sound signal, add reverb or echos, or, if a long delay is possible, enable musicians to record "loops". ''
Delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * ''The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and acto ...
/echo'': Delay/echo units produce an echo effect by adding a duplicate instrument-to-amplifier
electrical signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
to the original signal at a slight time-delay. The effect can either be a single echo called a "slap" or "slapback", or multiple echos. A well-known use of delay is the lead guitar in the U2 song "
Where the Streets Have No Name "Where the Streets Have No Name" is a song by Irish rock music, rock band U2. It is the opening track from their 1987 album ''The Joshua Tree'' and was released as the album's third single (music), single in August 1987. The song's hook (music) ...
", and also the opening riff of "
Welcome to the Jungle "Welcome to the Jungle" is a song by American rock band Guns N' Roses, featured on their debut album, ''Appetite for Destruction'' (1987). It was released as the album's second single initially in the UK in September 1987 then again in Octobe ...
" by Guns N' Roses. Delay effects: Boss DD-3 Digital Delay, MXR Carbon Copy,
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
Deluxe Memory Man, Line 6 DL4,
Roland RE-201 The Roland RE-201, commonly known as the Space Echo, is an audio effects unit that produces delay and reverb effects. It was produced by the Roland Corporation from 1974 to 1990. Background A tape echo device records incoming audio to a loop o ...
. ''Looper pedal'': A looper pedal or "phrase looper" allows a performer to record and later replay a phrase,
riff A riff is a repeated chord progression or refrain in music (also known as an ostinato figure in classical music); it is a pattern, or melody, often played by the rhythm section instruments or solo instrument, that forms the basis or acc ...
or passage from a song. Loops can be created on the spot during a performance (
live looping Live looping is the recording and playback of a piece of music in real-time using either dedicated hardware devices, called loopers or phrase samplers, or software running on a computer with an audio interface. Musicians can loop with either loo ...
) or they can be pre-recorded. By using a looper pedal, a singer-guitarist in a one person band can play the backing chords (or riffs) to a song, loop them with the pedal, and then sing and do a guitar solo over the chords. Some units allow a performer to layer multiple loops, enabling the performer to create the effect of a full band. The first loop effects were created with
reel-to-reel tape Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the ''supply reel'' (or ''feed reel'') containing the tape is plac ...
using a
tape loop In music, tape loops are loops of magnetic tape used to create repetitive, rhythmic musical patterns or dense layers of sound when played on a tape recorder. Originating in the 1940s with the work of Pierre Schaeffer, they were used among cont ...
. High-end boutique tape loop effects are still used by some studio producers who want a vintage sound. Digital loop effects recreate this effect using an electronic memory. ''
Reverb Reverberation (also known as reverb), in acoustics, is a persistence of sound, after a sound is produced. Reverberation is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is abs ...
'': Reverb units simulate the spacious sounds produced naturally in a huge stone cathedral (or other acoustic space such as a hall or room). This is done by creating a large number of echoes that gradually fade away in volume or "decay". One early technique for creating a reverb effect was to send an amplified signal of the music via a speaker to another room with reflective surfaces, such as a tile bathroom, and then record the natural reverberations that were produced. A plate reverb system uses an electromechanical
transducer A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another. Transducers are often employed at the boundaries of automation, measurement, and cont ...
to create vibrations in a plate of metal.
Spring reverb A reverb effect, or reverb, is an audio effect applied to a sound signal to simulate reverberation. It may be created through physical means, such as echo chambers, or electronically through audio signal processing. Echo chambers The first re ...
systems, which are often used in guitar amplifiers, use a transducer to create vibrations in a spring. Digital reverb effects use various
signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
s to create the reverb effect, often by using multiple feedback delay circuits.
Rockabilly Rockabilly is one of the earliest styles of rock and roll music. It dates back to the early 1950s in the United States, especially the South. As a genre it blends the sound of Western musical styles such as country with that of rhythm and blu ...
and
surf guitar Surf music (or surf rock, surf pop, or surf guitar) is a genre of rock music associated with surf culture, particularly as found in Southern California. It was especially popular from 1958 to 1964 in two major forms. The first is instrumental su ...
are two genres that make heavy use of reverb. Reverb effects:
Electro-Harmonix Electro-Harmonix (also commonly referred to as EHX) is a New York City-based company that makes electronic audio processors and sells rebranded vacuum tubes. The company was founded by Mike Matthews in 1968. It is best known for a series of gu ...
Holy Grail,
Fender Reverb Unit The Fender Reverb Unit (6G15) was a vacuum tube, spring reverb-equipped effects unit made by Fender. The Reverb Unit was originally introduced in 1961. It was discontinued in 1966 and was replaced by a solid-state model, the FR1000. The unit featur ...
.


Feedback/sustain

''
Audio feedback Audio feedback (also known as acoustic feedback, simply as feedback) is a positive feedback situation which may occur when an acoustic path exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for exa ...
'': Audio feedback is an effect produced when amplified sound is picked up by a microphone or guitar pickup and played back through a
guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
, initiating a "feedback loop", which usually consists of high-pitched sound. Feedback that occurs from a vocal mic into a
PA system A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound sou ...
is almost always avoided. However, in some styles of rock music, electric guitar players intentionally create feedback by playing their instrument directly in front of a heavily amplified, distorted
guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
's
speaker enclosure A loudspeaker enclosure or loudspeaker cabinet is an enclosure (often rectangular box-shaped) in which speaker drivers (e.g., loudspeakers and tweeters) and associated electronic hardware, such as crossover circuits and, in some cases, power ...
. The creative use of feedback effects was pioneered by guitarists such as Jimi Hendrix in the 1960s. This technique creates sustained, high-pitched
overtone An overtone is any resonant frequency above the fundamental frequency of a sound. (An overtone may or may not be a harmonic) In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental i ...
s and unusual sounds not possible through regular playing techniques. Guitar feedback effects can be difficult to perform, because it is difficult to determine the sound volume and guitar position relative to a guitar amp's loudspeaker necessary for achieving the desired feedback sound. Guitar feedback effects are used in a number of rock genres, including psychedelic rock, heavy metal music and punk rock.
EBow The EBow, short for electronic bow or energy bow, is an electronic device used for playing string instruments, most often the electric guitar. It is manufactured by Heet Sound Products, of Los Angeles, California. It was invented by Greg Heet i ...
is a
brand name A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...
of Heet Sound Products, of Los Angeles, California, for a small, handheld, battery-powered resonator. The Ebow was invented by Greg Heet, as a way to make a note on an electric guitar string resonate continuously, creating an effect that sounds similar to a bowed violin note or a sustained pipe organ note. The resonator uses a pickup – inductive string driver – feedback circuit, including a sensor coil, driver coil, and amplifier, to induce forced string resonance. The Ebow brand resonator is monophonic, and drives only one string at a time. Other handheld and mounted guitar and bass resonators have been on the market since the early 1990s, produced in Germany under the SRG brand, which ceased production in 2016, and were available in both monophonic (one string at a time) and polyphonic (multiple strings at a time) models, which included multiple onboard trigger switch effects, such as HPF (high pass filter) for enhancing harmonics and producing feedback effects, and LPF (low pass filter), producing a bass boost with a cello sound on heavy gauge strings. Later EBow models, such as the plus Ebow, contain a mode slide switch on the back, which allows the player to either produce just sustain or
overtone An overtone is any resonant frequency above the fundamental frequency of a sound. (An overtone may or may not be a harmonic) In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental i ...
feedback in addition to sustain. Pedals such as the Boss DF-2 and FB-2 use an internally generated signal matched to the pitch of the guitar that can be sustained indefinitely by depressing the pedal. Many compressor pedals are often also marketed as "sustainer pedals". As a note is sustained, it loses energy and volume due to diminishing vibration in the string. The compressor pedal boosts its electrical signal to the specified
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio between the largest and smallest values that a certain quantity can assume. It is often used in the context of Signal (electrical engineering), signals, like sound and light. It is measured ...
, slightly prolonging the duration of the note. This, combined with heavy distortion and the close proximity of the guitar and the speaker cabinet, can lead to infinite sustain at higher volumes.


Other effects

''Envelope follower'': An envelope follower activates an effect once a designated volume is reached. One effect that uses an envelope follower is the ''
auto-wah Auto-wah (also known as a "Q-wah", "T-wah", "envelope following filter", "envelope follower" or "envelope filter") is a type of wah-wah effects pedal typically used with electric guitar, bass guitar, clavinet, and electric piano etc. The distinc ...
'', which produces a "wah" effect depending on how loud or soft the notes are being played. ''
Guitar amplifier A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which ar ...
modeling'':
Amplifier modeling Amplifier modeling (also known as amp modeling or amp emulation) is the process of emulating a physical amplifier such as a guitar amplifier. Amplifier modeling often seeks to recreate the sound of one or more specific models of vacuum tube ampl ...
is a digital effect that replicates the sound of various amplifiers, most often vintage
tube amplifier A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal. Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by sol ...
s and famous brands of speaker cabinets (e.g., the
Ampeg SVT The Ampeg SVT is a bass guitar amplifier designed by Bill Hughes and Roger Cox for Ampeg and introduced in 1969. The SVT is a stand-alone amplifier or "head" as opposed to a "combo" unit comprising amp and speaker(s) in one cabinet, and was capab ...
8x10" bass cabinet). Sophisticated modeling effects can simulate different types of
speaker cabinet A loudspeaker enclosure or loudspeaker cabinet is an enclosure (often rectangular box-shaped) in which speaker drivers (e.g., loudspeakers and tweeters) and associated electronic hardware, such as crossover circuits and, in some cases, power a ...
s (e.g., the sound of an 8x10" cabinet) and
miking A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public ...
techniques. A rotary speaker simulator mimics the doppler and
chorus effect Chorus (or chorusing, choruser or chorused effect) is an audio effect that occurs when individual sounds with approximately the same time, and very similar pitches, converge. While similar sounds coming from multiple sources can occur naturally, ...
sound of a vintage Leslie speaker system by replicating its volume and pitch modulations, overdrive capacity and
phase shift In physics and mathematics, the phase of a periodic function F of some real variable t (such as time) is an angle-like quantity representing the fraction of the cycle covered up to t. It is denoted \phi(t) and expressed in such a scale that it ...
s. ''
Pitch correction Pitch correction is an electronic effects unit or audio software that changes the intonation (highness or lowness in pitch) of an audio signal so that all pitches will be notes from the equally tempered system (i.e., like the pitches on a piano) ...
/vocal effects'': Pitch correction effects use signal-processing algorithms to re-tune faulty intonation in a vocalist's performance or create unusual
vocoder A vocoder (, a portmanteau of ''voice'' and ''encoder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder was ...
-type vocal effects. One of the best known examples of this is
Autotune Auto-Tune (or autotune) is an audio processor introduced in 1996 by American company Antares Audio Technologies. Auto-Tune uses a proprietary device to measure and alter pitch in vocal and instrumental music recording and performances. Auto-T ...
, a software program and effect unit which can be used to both correct pitch (it moves a pitch to the nearest semitone), and add vocal effects. Some stompbox-style vocal pedals contain multiple effects, such as reverb and pitch correction. ''Simulators'': Simulators enable electric guitars to mimic the sound of other instruments such as acoustic guitar, electric bass and
sitar The sitar ( or ; ) is a plucked stringed instrument, originating from the Indian subcontinent, used in Hindustani classical music. The instrument was invented in medieval India, flourished in the 18th century, and arrived at its present form ...
. Pick up simulators used on guitars with
single-coil A single coil pickup is a type of magnetic transducer, or pickup, for the electric guitar and the electric bass. It electromagnetically converts the vibration of the strings to an electric signal. Single coil pickups are one of the two most po ...
pick ups replicate the sound of guitars with
humbucker A humbucking pickup, humbucker, or double coil, is a type of guitar pickup that uses two wire coils to cancel out the noisy interference picked up by coil pickups. In addition to electric guitar pickups, humbucking coils are sometimes used in ...
pick ups, or vice versa. A de- fretter is a bass guitar effect that simulates the sound of a
fretless bass A fretless bass is a bass guitar whose neck does not have any frets. While the instrument is played in all styles of music, it is most common in pop, rock, and jazz. It first saw widespread use during the 1970s, although some players used them befo ...
. The effect uses an envelope-controlled filter and
voltage-controlled amplifier A variable-gain (VGA) or voltage-controlled amplifier (VCA) is an electronic amplifier that varies its gain depending on a control voltage (often abbreviated CV). VCAs have many applications, including audio level compression, synthesizers and ...
to "soften" a note's attack both in volume and
timbre In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or tone. Timbre distinguishes different types of sound production, such as choir voices and musica ...
. ''
Bitcrusher A Bitcrusher is an audio effect that produces distortion by reducing of the resolution or bandwidth of digital audio data. The resulting quantization noise may produce a "warmer" sound impression, or a harsh one, depending on the amount of reduct ...
filters'': Bitcrushers rely on conversion of the audio signal into a digital format (ADC) and the reduction of sound fidelity by utilising bit (and sometimes sample) rates low enough to cause significant colouration and filtering within the audible frequency range. '' Rotating speakers'' are specially constructed
amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
or
loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or ...
s used to create special audio effects using the Doppler effect by rotating the speakers or a sound-directing duct. The rotating speaker creates a chorus-type effect. Named after its inventor,
Donald Leslie Donald James Leslie (April 13, 1911 – September 2, 2004) created and manufactured the Leslie speaker that refined the sound of the Hammond organ and helped popularize electronic music. Leslie experimented with devices to, in his words, improve ...
, it is particularly associated with the Hammond organ but is used with a variety of instruments as well as vocals. The Hammond/Leslie combination has become an element in many genres of music. The Leslie Speaker and the Hammond Organ brands are currently owned by Suzuki Musical Instrument Corporation. The stompbox that simulates this effect is the
Uni-Vibe The Uni-Vibe, also marketed as the Jax Vibra-Chorus,Harry Shapiro, Michael Heatley, Roger Mayer''Jimi Hendrix Gear'', page 120 Voyageur Press is a footpedal-operated phaser or phase shifter for creating chorus and vibrato simulations for elec ...
pedal. The ''
Korg Kaoss Pad The Kaoss Pad is an audio sampling instrument and multi-effects processor originally launched by Korg in 1999. It allows users to record and process audio samples and apply various effects using an X-Y touchscreen. Features Kaoss Pads allow use ...
'' is a small
touchpad A touchpad or trackpad is a pointing device featuring a tactile sensor, a specialized surface that can translate the motion and position of a user's fingers to a relative position on the operating system that is made output to the screen. Touchp ...
MIDI MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
controller, sampler, and effects processor for audio and musical instruments, made by
Korg , founded as Keio Electronic Laboratories, is a Japanese multinational corporation that manufactures electronic musical instruments, audio processors and guitar pedals, recording equipment, and electronic tuners. Under the Vox brand name, th ...
. The Kaoss Pad's touchpad can be used to control its internal effects engine, which can be applied to a line-in signal or to samples recorded from the line-in. Effects types include pitch shifting,
distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signa ...
, filtering, wah-wah, tremolo,
flanging Flanging is an audio effect produced by mixing two identical signals together, one signal delayed by a small and (usually) gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and no ...
,
delay Delay (from Latin: dilatio) may refer to: Arts, entertainment, and media * ''Delay 1968'', a 1981 album by German experimental rock band Can * ''The Delay'', a 2012 Uruguayan film People * B. H. DeLay (1891–1923), American aviator and acto ...
, reverberation, auto-panning, gating,
phasing A phaser is an electronic sound processor used to filter a signal, and it has a series of troughs in its frequency-attenutation graph. The position (in Hz) of the peaks and troughs are typically modulated by an internal low-frequency oscil ...
, and
ring modulation In electronics, ring modulation is a signal processing function, an implementation of frequency mixing, in which two signals are combined to yield an output signal. One signal, called the carrier, is typically a sine wave or another simple ...
. The Kaoss Pad can also be used as a
MIDI controller A MIDI controller is any hardware or software that generates and transmits Musical Instrument Digital Interface (MIDI) data to MIDI-enabled devices, typically to trigger sounds and control parameters of an electronic music performance. They mos ...
.


Bass effects

Bass effects Bass effects are electronic effects units that are designed for use with an electric bass and a bass amplifier, or for an upright bass and a bass amp or PA system. Bass effects are commonly available in stompbox-style pedals, which are metal or ...
are electronic effects units that are designed for use with the low pitches created by an electric bass or for an
upright bass The double bass (), also known simply as the bass () (or by other names), is the largest and lowest-pitched bowed (or plucked) string instrument in the modern symphony orchestra (excluding unorthodox additions such as the octobass). Similar ...
used with a bass amp or
PA system A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound sou ...
. Two examples of bass effects are
fuzz bass Fuzz bass is a style of playing the electric bass or modifying its signal that produces a buzzy, distorted, overdriven sound, as the name implies. Overdriving a bass signal significantly changes the timbre, adds higher overtones (harmonics) ...
and bass chorus. Some
bass amplifier A bass amplifier (also abbreviated to bass amp) is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audien ...
s have built-in effects, such as overdrive or
chorus Chorus may refer to: Music * Chorus (song) or refrain, line or lines that are repeated in music or in verse * Chorus effect, the perception of similar sounds from multiple sources as a single, richer sound * Chorus form, song in which all verse ...
.
Upright bass The double bass (), also known simply as the bass () (or by other names), is the largest and lowest-pitched bowed (or plucked) string instrument in the modern symphony orchestra (excluding unorthodox additions such as the octobass). Similar ...
ists in jazz, folk, blues and similar genres may use a bass
preamplifier A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier a ...
, a small electronic device that matches the impedance between the
piezoelectric pickup A pickup is a transducer that captures or senses mechanical vibrations produced by musical instruments, particularly stringed instruments such as the electric guitar, and converts these to an electrical signal that is amplified using an instru ...
and the amp or PA system. Bass preamps also allow for the gain of the signal to be boosted or cut. Some models also offer equalization controls, a compressor, and a
DI box A DI unit (direct input or direct inject) is an electronic device typically used in recording studios and in sound reinforcement systems to connect a high- output impedance, line level, unbalanced output signal to a low-impedance, microphone le ...
connection.


Boutique pedals

Boutique pedals are designed by smaller, independent companies and are typically produced in limited quantities. Some may even be hand-made, with hand-soldered connections. These pedals are mainly distributed online or through mail-order, or sold in a few music stores. They are often more expensive than mass-produced pedals and offer higher-quality components, innovative designs, in-house-made knobs, and hand-painted artwork or etching. Some boutique companies focus on re-creating classic or vintage effects. Some boutique pedal manufacturers include:
BJFE BJFE Guitar Effects is a company which manufactures effects pedals for use with instruments such as an electric guitar. These pedals are commonly used by guitarists to modify the sound of their guitar before it reaches the amp. The company is ...
, Pete Cornish,
Emlyn Crowther Paul Emlyn Crowther (born 2 October 1949 in Dunedin, New Zealand) is the former drummer of Split Enz who performed with the band from July 1974 to November 1976. Before joining the Enz, Crowther played trumpet in an air training corp band but ...
,
Death By Audio Death By Audio was a warehouse space on the first floor of an industrial building in the Williamsburg neighborhood of Brooklyn, New York. The warehouse took its name from the boutique effects pedal company, Death By Audio, based in the space. Th ...
, Robert Keeley, Roger Linn, Roger Mayer, Strymon, T-Rex Engineering, ToadWorks and Z.Vex Effects.


Modification

There is also a niche market for modifying or "modding" effects. Typically, vendors provide either custom modification services or sell new effects pedals they have already modified. The
Ibanez Tube Screamer The Ibanez Tube Screamer (TS808/TS9) is a guitar overdrive pedal, made by Ibanez. The pedal has a characteristic mid-boosted tone popular with blues, rock and metal players. The Tube Screamer has been used by many guitarists to create their signa ...
,
Boss DS-1 The Boss DS-1 is a distortion pedal for guitar, manufactured by the Roland Corporation under the brand name Boss since 1978. The first distortion effects unit made by Boss, it has become a classic effect, used by many notable guitar players. B ...
,
Pro Co RAT The Pro Co "The RAT" is a distortion pedal produced by Pro Co Sound. The original RAT was developed in the basement of Pro Co's Kalamazoo, Michigan facility in 1978. Numerous variations of the original RAT pedal are still being produced today. The ...
and
DigiTech Whammy The DigiTech Whammy is a pitch shifter pedal manufactured by DigiTech. It was the first widely used effects pedal that could do foot-controlled pitch shifting effects. The pedal emulates sounds that a guitarist normally makes using the vibrato ...
are some of the most often-modified effects. Common modifications include value changes in capacitors or resistors, adding true-bypass so that the effect's circuitry is no longer in the signal path, substituting higher-quality components, replacing the unit's original operational amplifiers (op-amps), or adding functions to the device, such as allowing additional control of some factor or adding another output jack.


Other pedals and rackmount units

Not all stompboxes and rackmounted electronic devices designed for musicians are effects. Strobe tuner and regular
electronic tuner In music, an electronic tuner is a device that detects and displays the pitch of musical notes played on a musical instrument. "Pitch" is the perceived fundamental frequency of a musical note, which is typically measured in Hertz. Simple tuner ...
pedals indicate whether a guitar string is too
sharp Sharp or SHARP may refer to: Acronyms * SHARP (helmet ratings) (Safety Helmet Assessment and Rating Programme), a British motorcycle helmet safety rating scheme * Self Help Addiction Recovery Program, a charitable organisation founded in 19 ...
or
flat Flat or flats may refer to: Architecture * Flat (housing), an apartment in the United Kingdom, Ireland, Australia and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), ...
. Stompbox-format tuner pedals route the electric signal for the instrument through the unit via a 1/4" patch cable. These pedal-style tuners usually have an output so that the signal can be plugged into a
guitar amp A guitar amplifier (or amp) is an electronic device or system that strengthens the electrical signal from a pickup on an electric guitar, bass guitar, or acoustic guitar so that it can produce sound through one or more loudspeakers, which a ...
to produce sound. Rackmount
power conditioner A power conditioner (also known as a line conditioner or power line conditioner) is a device intended to improve the quality of the power that is delivered to electrical load equipment. The term most often refers to a device that acts in one or ...
devices deliver a voltage of the proper level and characteristics to enable equipment to function properly (e.g., by providing transient impulse protection). A rackmounted wireless receiver unit is used to enable a guitarist or bassist to move around on stage without being connected to a cable. A footswitch pedal such as the "A/B" pedal routes a guitar signal to an amplifier or enables a performer to switch between two guitars, or between two amplifiers. Guitar amplifiers and
electronic keyboards An electronic keyboard, portable keyboard, or digital keyboard is an electronic musical instrument, an electronic derivative of keyboard instruments. Electronic keyboards include synthesizers, digital pianos, stage pianos, electronic organs ...
may have switch pedals for turning built-in reverb and distortion effects on and off; the pedals contain only a switch, with the circuitry for the effect being housed in the amplifier chassis. Some musicians who use rackmounted effects or laptops employ a
MIDI MIDI (; Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and ...
controller pedalboard or armband remote controls to trigger sound samples, switch between different effects or control effect settings. A pedal keyboard uses pedals, but it is not an effect unit; it is a foot-operated keyboard in which the pedals are typically used to play basslines.


See also

* — a list of non-electronic audio effects * :Audio effects *
Frequency divider A frequency divider, also called a clock divider or scaler or prescaler, is a circuit that takes an input signal of a frequency, f_, and generates an output signal of a frequency: : f_ = \frac where n is an integer. Phase-locked loop frequency ...
*
Frequency mixer In electronics, a mixer, or frequency mixer, is an electrical circuit that creates new frequencies from two signals applied to it. In its most common application, two signals are applied to a mixer, and it produces new signals at the sum and di ...
*
Nonlinear filter In signal processing, a nonlinear (or non-linear) filter is a filter whose output is not a linear function of its input. That is, if the filter outputs signals ''R'' and ''S'' for two input signals ''r'' and ''s'' separately, but does not always o ...
*
Outboard gear Musical outboard equipment or outboard gear is used to process or alter a sound signal separately from functionality provided within a mixing console or a digital audio workstation. Outboard effects units can be used either during a live performanc ...
— effects units used in the context of
audio mixing Audio mixing is the process by which multiple sounds are combined into one or more channels. In the process, a source's volume level, frequency content, dynamics, and panoramic position are manipulated or enhanced. This practical, aesthetic ...
*
Sound effect A sound effect (or audio effect) is an artificially created or enhanced sound, or sound process used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media. Traditi ...
*
Vintage musical equipment Vintage musical equipment is older music gear, including instruments, amplifiers and speakers, sound recording equipment and effects pedals, sought after, maintained and used by record producers, audio engineers and musicians who are interested ...


References

{{DEFAULTSORT:Effects Unit Electric guitars Guitars Sound recording Rock music Sound effects Pedals