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 Westernmusical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the interval of an octave. Depressing a key on the keyboard makes the instrument produce sounds, either by making a hammer mechanically strike a string or 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 (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 triggers a sound. A pedal keyboard is a keyboard played with the feet, usually used with a pipe organ or theatre organ. Since the most commonly encountered keyboard instrument is the piano, the keyboard layout is often referred to as the "piano keyboard".
Musical keyboards can have as few as 12 keys, as in the case of the pedal keyboards used with spinet organs, 25 keys with 2010-era MIDI controller keyboards, 61 keys for many home keyboards, and 88 keys for an acoustic piano. Some keyboards have two ranks of keyboards, one above the other, with the two keyboards referred to as the lower and upper manual, such as the Hammond organ, pipe organs and some harpsichords. Some pipe organs and theatre organs may have three keyboards. Pedal keyboards have from 12 keys (home spinet organs) to 32 or more (pipe organs in churches).