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Mastering, a form of
audio post production Audio post production is all stages of audio production relating to sound produced and synchronized with moving picture (film, television, or video). It involves sound design, Sound effect, sound effects, Foley (filmmaking), Foley, Dubbing (filmmaki ...
, is the process of preparing and transferring recorded audio from a source containing the final mix to a
data storage device Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, Phonograph record, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Some authors even propose that DNA ...
(the master), the source from which all copies will be produced (via methods such as pressing, duplication or replication). In recent years
digital master A digital master is an image An SAR radar imaging, radar image acquired by the SIR-C/X-SAR radar on board the Space Shuttle Endeavour shows the Teide volcano. The city of Santa Cruz de Tenerife is visible as the purple and white area on the ...
s have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering. Mastering requires critical listening; however, software tools exist to facilitate the process. Results depend upon the intent of the engineer, the skills of the engineer, the accuracy of the speaker monitors, and the listening environment.
Mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital domain as mono, stereo STEREO (Solar Terrestrial Relations Observatory) is a S ...
s often apply equalization and
dynamic range compression Dynamic range compression (DRC) or simply compression is an audio signal processing Audio signal processing is a subfield of that is concerned with the electronic manipulation of s. Audio signals are electronic representations of s—s ...
in order to optimize sound translation on all playback systems. It is standard practice to make a copy of a master recording—known as a safety copy—in case the master is lost, damaged or stolen.


History


Pre-1940s

In the earliest days of the recording industry, all phases of the recording and mastering process were entirely achieved by mechanical processes. Performers sang and/or played into a large acoustic horn and the master recording was created by the direct transfer of acoustic energy from the
diaphragm Diaphragm may refer to: * Diaphragm (anatomy) or thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Diaphragm (optics), a stop in the light path of a lens, having an aperture that regulates the amount of light that pass ...
of the recording horn to the mastering lathe, typically located in an adjoining room. The cutting head, driven by the energy transferred from the horn, inscribed a modulated groove into the surface of a rotating cylinder or disc. These masters were usually made from either a soft metal alloy or from
wax Waxes are a diverse class of organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prope ...
; this gave rise to the colloquial term ''waxing'', referring to the cutting of a record. After the introduction of the
microphone A microphone, colloquially called a mic or mike (), is a device – a transducer A transducer is a device that energy from one form to another. Usually a transducer converts a in one form of energy to a signal in another. Transducers ar ...

microphone
and
electronic amplifier An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the power Power typically refers to: * Power (physics) In physics, power is the amount of energy transferred or converted per unit time. In ...

electronic amplifier
in the mid-1920s, the mastering process became electro-mechanical, and electrically driven mastering lathes came into use for cutting master discs (the cylinder format by then having been superseded). Until the introduction of tape recording, master recordings were almost always cut direct-to-disc. Only a small minority of recordings were mastered using previously recorded material sourced from other discs.


Emergence of magnetic tape

In the late 1940s, the recording industry was revolutionized by the introduction of
magnetic tape Magnetic tape is a medium for , made of a thin, magnetizable coating on a long, narrow strip of . It was developed in Germany in 1928, based on . Devices that record and playback audio and video using magnetic tape are s and s respectively. A ...

magnetic tape
. Magnetic tape was invented for recording sound by
Fritz Pfleumer Fritz Pfleumer (20 March 1881 – 29 August 1945) was a German engineer Engineers, as practitioners of engineering, are Professional, professionals who Invention, invent, design, analyze, build and test Machine, machines, complex systems, arch ...
in 1928 in Germany, based on the invention of
magnetic wire recording Poulsen Telegraphone recorder from 1922 Wire recording or magnetic wire recording was the first magnetic recording technology, an analog signal, analog type of audio storage in which a magnetic recording is made on a thin steel wire. The first ...
by
Valdemar Poulsen Valdemar Poulsen (23 November 1869 – 23 July 1942) was a Danish engineer Engineers, as practitioners of engineering, are Professional, professionals who Invention, invent, design, analyze, build and test Machine, machines, complex systems, a ...
in 1898. Not until the end of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a global war A world war is "a war War is an intense armed conflict between states State may refer to: Arts, entertainment, and media Literatur ...
could the technology be found outside Europe. The introduction of magnetic tape recording enabled master discs to be cut separately in time and space from the actual recording process. Although tape and other technical advances dramatically improved the audio quality of commercial recordings in the post-war years, the basic constraints of the electro-mechanical mastering process remained, and the inherent physical limitations of the main commercial recording media—the 78 rpm disc and later the 7-inch 45 rpm single and 33-1/3 rpm
LP record The LP (from "long playing" or "long play") is an analog sound storage medium, a phonograph record format characterized by: a speed of  revolutions per minute, rpm; a 12- or 10-inch (30- or 25-cm) diameter; use of the "microgroove" gro ...
—meant that the audio quality,
dynamic range Dynamic range (abbreviated DR, DNR, or DYR) is the ratio In mathematics, a ratio indicates how many times one number contains another. For example, if there are eight oranges and six lemons in a bowl of fruit, then the ratio of oranges to lem ...
, and running time of master discs were still limited compared to later media such as the
compact disc The compact disc (CD) is a digital Digital usually refers to something using digits, particularly binary digits. Technology and computing Hardware *Digital electronics Digital electronics is a field of electronics Electronics compri ...

compact disc
.


Electro-mechanical mastering process

From the 1950s until the advent of digital recording in the late 1970s, the mastering process typically went through several stages. Once the studio recording on multi-track tape was complete, a final
mix MIX is a hypothetical computer used in Donald Knuth's monograph, '' The Art of Computer Programming'' (''TAOCP''). MIX's model number is 1009, which was derived by combining the model numbers and names of several contemporaneous, commercial machi ...
was prepared and dubbed down to the master tape, usually either a single-track or two-track
stereo File:Carsoundstereoshift.png, Time difference in a stereophonic recording of a car going past, 250px Stereophonic sound or, more commonly, stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible per ...

stereo
tape. Prior to the cutting of the master disc, the master tape was often subjected to further electronic treatment by a specialist
mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital domain as mono, stereo STEREO (Solar Terrestrial Relations Observatory) is a S ...
. After the advent of tape it was found that, especially for pop recordings, master recordings could be made so that the resulting record would sound better. This was done by making fine adjustments to the amplitude of sound at different frequency bands ( equalization) prior to the cutting of the master disc. In large recording companies such as
EMI EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British transnational conglomerate Conglomerate or conglomeration may refer to: * Conglomerate (compan ...
, the mastering process was usually controlled by specialist staff technicians who were conservative in their work practices. These big companies were often reluctant to make changes to their recording and production processes. For example, EMI was very slow in taking up innovations in
multi-track recording Digital audio interface for the Pro Tools computer-based hard disk multitrack recording system. Digital audio quality is measured in data resolution per channel. Multitrack recording (MTR), also known as multitracking or tracking, is a method o ...
and did not install 8-track recorders in their
Abbey Road Studios Abbey Road Studios (formerly EMI Recording Studios) is a recording studio at 3 Abbey Road ''Abbey Road'' is the eleventh studio album by the English Rock music, rock band the Beatles, released on 26 September 1969 by Apple Records. Nam ...

Abbey Road Studios
until the late 1960s, more than a decade after the first commercial 8-track recorders were installed by American independent studios.


Digital technology

In the 1990s, electro-mechanical processes were largely superseded by digital technology, with digital recordings stored on
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device On a reel-to-reel tape recorder (Sony TC-630), the recorder is data storage equipment and the magnetic tape is a data stora ...

hard disk drive
s or digital tape and mastered to . The
digital audio workstation A digital audio workstation (DAW) is an electronic device or application software Application software (app for short) is computing software designed to carry out a specific task other than one relating to the operation of the computer itsel ...
(DAW) became common in many mastering facilities, allowing the off-line manipulation of recorded audio via a
graphical user interface The graphical user interface (GUI "UI" by itself is still usually pronounced . or ) is a form of user interface In the industrial design Industrial design is a process of design A design is a plan or specification for the construction ...
(GUI). Although many digital processing tools are common during mastering, it is also very common to use analog media and processing equipment for the mastering stage. Just as in other areas of audio, the benefits and drawbacks of digital technology compared to analog technology are still a matter for debate. However, in the field of audio mastering, the debate is usually over the use of digital versus analog signal processing rather than the use of digital technology for storage of audio. Digital systems have higher performance and allow mixing to be performed at lower maximum levels. With peaks between -3 and -9 dBFS on a mix, the mastering engineer has enough headroom to process and produce a final master.Bob Katz Mixing Tips
It is important to allow enough headroom for the mastering engineer's work. Reduction of headroom by the mix or mastering engineer has resulted in a
loudness war The loudness war (or loudness race) is a trend of increasing audio levels in recorded music, which reduces audio fidelity and — according to many critics — listener enjoyment. Increasing loudness was first reported as early as the 1940s, wi ...
in commercial recordings.


Process

The source material, ideally at the original resolution, is processed using equalization,
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 co ...
,
limiting In electronics, a limiter is a circuit that allows signals below a specified input power or level to pass unaffected while Attenuator (electronics), attenuating (lowering) the peaks of stronger signals that exceed this threshold. Limiting is a t ...
and other processes. Additional operations, such as editing, specifying the gaps between tracks, adjusting level, fading in and out,
noise reduction Noise reduction is the process of removing noise Noise is unwanted sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psycholo ...
and other signal restoration and enhancement processes can also be applied as part of the mastering stage. The source material is put in the proper order, commonly referred to as assembly (or 'track') sequencing. These operations prepare the music for either digital or analog, e.g. vinyl, replication. If the material is destined for vinyl release, additional processing, such as dynamic range reduction or frequency-dependent stereo–to–mono fold-down and equalization may be applied to compensate for the limitations of that medium. For compact disc release, ''start of track'', ''end of track'', and ''indexes'' are defined for playback navigation along with
International Standard Recording Code The International Standard Recording Code (ISRC) is an international standard code for uniquely identifying sound recordings and music video recordings. The code was developed by the recording industry in conjunction with the ISO The Internati ...
(ISRC) and other information necessary to replicate a CD. Vinyl LP and cassettes have their own pre-duplication requirements for a finished master. Subsequently, it is rendered either to a physical medium, such as a CD-R or DVD-R, or to computer files, such as a Disc Description Protocol (DDP) file set or an
ISO image An optical disc image (or ISO image, from the ISO 9660 ISO 9660 is a file system In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation ...
. Regardless of what delivery method is chosen, the replicator factory will transfer the audio to a
glass master In optical disc manufacturing, replication is the process of producing discs via methods that do not involve "burning" blank CD, DVD or other discs; the latter is known as Optical disc authoring, duplication. The replication of optical discs invol ...
that will generate metal stampers for replication. The process of audio mastering varies depending on the specific needs of the audio to be processed. Mastering engineers need to examine the types of input media, the expectations of the source producer or recipient, the limitations of the end medium and process the subject accordingly. General rules of thumb can rarely be applied. Steps of the process typically include the following: # Transferring the recorded audio tracks into the Digital Audio Workstation (DAW) # Sequence the separate songs or tracks as they will appear on the final release # Adjust the length of the silence between songs # Process or sweeten audio to maximize the sound quality for the intended medium (e.g. applying specific EQ for vinyl) # Transfer the audio to the final master format (CD-ROM, half-inch reel tape, PCM 1630 U-matic tape, etc.) Examples of possible actions taken during mastering: # Editing minor flaws # Applying
noise reduction Noise reduction is the process of removing noise Noise is unwanted sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psycholo ...

noise reduction
to eliminate clicks, dropouts, hum and hiss # Adjusting stereo width # Equalize audio across tracks for the purpose of optimized frequency distribution # Adjust volume # Dynamic range compression or expansion # # Inserting ISRC codes and CD text # Arranging track in their final sequential order # Fading out the ending of each song (if required) #
Dither Dither is an intentionally applied form of noise Noise is unwanted sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psyc ...

Dither


Notable audio mastering engineers

*
Bernie Grundman Bernie Grundman is an American audio engineering, audio engineer. He is most known for his audio mastering, mastering work and his studio, Bernie Grundman Mastering, which he opened in 1983 in Hollywood. The studio, which includes engineers Chris ...
* Bob Katz *
Bob Ludwig Robert C. Ludwig (born c. 1945) is an American mastering engineer. He has mastered recordings on all the major Audio format, recording formats for all the major record labels, and on projects by more than 1,300 artists including Led Zeppelin, Qu ...
*
Greg Calbi Gregory Calbi (born April 3, 1949) is an American mastering engineer at Sterling Sound, New Jersey New Jersey is a U.S. state, state in the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the ...

Greg Calbi
*
Chris Gehringer Chris Gehringer (born May 27, 1962) is an American mastering engineer, known for having mastered recordings such as Rihanna's '' Loud'', Lady Gaga's '' Born This Way'', and Drake's '' Take Care''. Biography Gehringer was born in Teaneck, New J ...

Chris Gehringer
*
Doug Sax Doug Sax (April 26, 1936 – April 2, 2015) was an American mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital do ...

Doug Sax
* Eric Pillai *
George Marino George Marino (April 15, 1947 – June 4, 2012) was an American mastering engineer known for working on albums by rock bands starting in the late 1960s. Biography Marino was born on April 15, 1947 in the New York City borough The Bronx The B ...

George Marino
* George "Porky" Peckham *
H. Sridhar H. Sridhar (Sridhar Hariharan/H.Padmanabh) was a sound engineer from India and known for his work with the Indian Musician A R Rahman. Sridhar was the Chief Audio Engineer at Media Artists Chennai. A mathematics graduate, with keen interest in e ...
*
Howie Weinberg Howie Weinberg is an American mastering engineer. He has over 200 Gold Gold is a chemical element with the Symbol (chemistry), symbol Au (from la, aurum) and atomic number 79, making it one of the higher atomic number elements that occur n ...
* Mandy Parnell * P. A. Deepak * Shadab Rayeen *
Tony Dawsey Tony Dawsey is mastering engineer at Masterdisk Masterdisk is an American multimedia company in New York, located at 8 John Walsh Boulevard in Peekskill. They provide production services such as audio mastering, vinyl cutting and enhanced CD a ...
*
Emily Lazar Emily B. Lazar is an American mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital domain as mono, stereo STERE ...
* Steve Hoffman * Randy Merrill *
Leon Zervos Leon Zervos is a mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the analog or digital domain as mono, stereo STEREO (Solar ...

Leon Zervos
*
Stephen Marcussen Stephen Marcussen is the founder and chief mastering engineer at Marcussen Mastering in Hollywood, California Hollywood is a neighborhood A neighbourhood (British English British English (BrE) is the standard dialect of the Engli ...
*
Ray Staff Ray Staff is a British mastering engineer, best known for his work with a diverse mix of artists including Led Zeppelin, The Rolling Stones, The Clash and Black Sabbath. Most recently he has mastered albums for Muse (band), Muse. Biography and ...
*
Ted Jensen Ted Jensen (born September 19, 1954) is an American mastering engineer, known for having mastered many recordings, including the Eagles' '' Hotel California'', Green Day's '' American Idiot'' and Norah Jones' '' Come Away with Me''. Biograph ...

Ted Jensen
* Brad Blackwood *
Brian Gardner Brian Knapp Gardner, also known as Brian "Big Bass" Gardner, is an American mastering engineer A mastering engineer is a person skilled in the practice of taking audio (typically musical content) that has been previously mixed in either the ana ...
*
George Marino George Marino (April 15, 1947 – June 4, 2012) was an American mastering engineer known for working on albums by rock bands starting in the late 1960s. Biography Marino was born on April 15, 1947 in the New York City borough The Bronx The B ...

George Marino


See also

*
Album era The album era was a period in English-language popular music Popular music is music with wide appeal that is typically distributed to large audiences through the music industry. These forms and styles can be enjoyed and performed by people ...
*
Remaster Remaster (also digital remastering and digitally remastered) refers to changing the quality of the sound or of the image, or both, of previously created recordings, either audiophonic, cinematic, or videographic. Mastering A master is the defi ...
* 2008 Universal Studios fire


Notes


References

{{DEFAULTSORT:Audio Mastering Audio engineering Optical disc authoring Sound recording Music industry