Keyboard instruments are often classified as percussion instruments in an orchestra because they are played by striking the keys, and can often play an important rhythmic role in some music. However, unlike other percussion instruments, their sound is not produced by the vibration of a membrane or solid material.

Sound is produced on the piano when a player presses the keys, which causes small hammers to strike the strings inside the instrument.  It is the vibrations of the piano's strings which produces its musical sound.