A carillon ( KARR-ə-lon, kə-RIL-yən) is a pitched percussion instrument that is played with a keyboard and consists of at least 23 bells. The bells are cast in bronze, hung in fixed suspension, and tuned in chromatic order so that they can be sounded harmoniously together. They are struck with clappers connected to a keyboard of wooden batons played with the hands and pedals played with the feet. Often housed in bell towers, carillons are usually owned by churches, universities, or municipalities. They can include an automatic system through which the time is announced and simple tunes are played throughout the day.

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. Pressing a key on the keyboard makes the instrument produce sounds—either by mechanically striking a string or tine, plucking a string (harpsichord), causing air to flow through a pipe organ, striking a bell (carillon), or activating an electronic circuit. Since the most commonly encountered keyboard instrument is the piano, the keyboard layout is often referred to as the piano keyboard or simply piano keys.