On a piano, organ, harpsichord, virginal, etc., the keys are the levers which the performer depresses to activate the action, thus producing tones.On a woodwind instrument, the keys are the metal disks that close or open soundholes by means of levers operated by the performer's fingers. Keys are used for those soundholes that are uncomfortable or impossible for the performer to reach with his fingers.A specific scale or series of notes defining a particular tonality. Keys may be defined as major or minor, and are named after their tonic or keynote. Thus the series of notes with intervals defining a major tonality and based on the key of C is the key of C major. Music that is based on a major or minor scale is said to be in a key. Keys are identified by their tonic.(1) tonality, the tonal center of a composition (2) the initial component of the action chain of a keyboard, the part that is struck with the fingers (3) the levers controlling the covers for sound holes of a wind instrument<br><br>Music that is based on a major or minor scale is said to be in a key. Keys are identified by their tonic<br><br>In piston valves, a small projection from the side of the piston which runs in a groove or `keyway' on the inside of the valve casing and keeps the piston in the correct alignment<br><br>The control of a dynamics processing device by an external audio signal. Also refers to the "key" that music is in, as in the Key of C.