A key is a specific part of a musical instrument. The purpose and function of the part in question depend on the instrument. On instruments equipped with tuning machines such as

guitar The guitar is a fretted musical instrument that typically has six strings. It is usually held flat against the player's body and played by strumming or plucking the strings with the dominant hand, while simultaneously pressing selected strin ...

s or mandolins, a key is part of a

tuning machine A machine head (also referred to as a tuning machine, tuner, or gear head) is a geared apparatus for tuning stringed musical instruments by adjusting string tension. Machine heads are used on mandolins, guitars, double basses and others, and ar ...

. It is a worm gear with a key shaped end used to turn a cog, which, in turn, is attached to a post which winds the string. The key is used to make pitch adjustments to a string. With other instruments,

zither Zithers (; , from the Greek word ''cithara'') are a class of stringed instruments. Historically, the name has been applied to any instrument of the psaltery family, or to an instrument consisting of many strings stretched across a thin, flat ...

s and drums, for example, a key is essentially a small wrench used to turn a tuning machine or lug. On

woodwind Woodwind instruments are a family of musical instruments within the greater category of wind instruments. Common examples include flute, clarinet, oboe, bassoon, and saxophone. There are two main types of woodwind instruments: flutes and re ...

instruments such as a flute or

saxophone The saxophone (often referred to colloquially as the sax) is a type of Single-reed instrument, single-reed woodwind instrument with a conical body, usually made of brass. As with all single-reed instruments, sound is produced when a reed (mouthpi ...

, keys are finger operated levers used to open or close tone holes, thereby shortening or lengthening the resonating tube of the instrument. The keys on the keyboard of a pipe organ also open and close various valves, but the airflow is driven mechanically rather than lung powered, and the flow of air is directed through different pipes tuned for each note. The keys of an accordion direct the air flow from manually operated

bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtig ...

across various tuned vibrating reeds. On other

keyboard instrument A keyboard instrument is a musical instrument played using a keyboard, a row of levers which are pressed by the fingers. The most common of these are the piano, organ, and various electronic keyboards, including synthesizers and digital p ...

s, a key may be a lever which mechanically triggers a hammer to strike a group of strings, as on a

piano The piano is a stringed keyboard instrument in which the strings are struck by wooden hammers that are coated with a softer material (modern hammers are covered with dense wool felt; some early pianos used leather). It is played using a keybo ...

, or an electric switch which energizes an

audio oscillator An electronic oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave or a triangle wave. Oscillators convert direct current (DC) from a power supply to an alternating ...

as on an

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 ...

or a synthesizer.

See also