A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the interval of an octave. Depressing or striking a key on the keyboard makes the instrument produce sounds, either by making a hammer mechanically strike a string or metal tine (piano, electric piano, clavichord); pluck a string (harpsichord); open a valve to let air flow through a pipe (pipe organ or accordion); or strike a bell (a carillon in a church tower). On electric and electronic keyboards, depressing a key connects one or more circuits (Hammond organ, digital piano, synthesizer, MIDI controller keyboard), which tri