Which musical instrument commonly features 88 keys?

The piano is a musical instrument that is traditionally equipped with 88 keys, which consist of 52 white keys and 36 black keys. These keys enable pianists to produce a wide range of musical notes, from deep bass sounds to high treble tones. The design of the keyboard allows for both melody and harmony to be played simultaneously, making the piano a versatile instrument in various musical genres.

In contrast, a guitar has six strings and uses frets rather than keys to produce notes, while a violin has four strings and is played with a bow or by plucking. The flute, a woodwind instrument, does not have keys in the same sense. Instead, it has finger holes and keys that allow players to cover holes to produce different pitches. Therefore, among the listed options, the piano is uniquely identified by its 88-key layout, which is fundamental to its identity and function in music.