Organ

The organ is a keyboard instrument of one or more pipe divisions or other means for producing tones, each played with its own keyboard, played either with the hands on a keyboard or with the feet using pedals. The organ is a relatively old musical instrument,  dating from the time of Ctesibius of Alexandria (285–222 BC), who invented the water organ. It was played throughout the Ancient Greek and Ancient Roman world, particularly during races and games. During the early medieval period it spread from the Byzantine Empire, where it continued to be used in secular (non-religious) and imperial court music, to Western Europe, where it gradually assumed a prominent place in the liturgy of the Catholic Church. Subsequently it re-emerged as a secular and recital instrument in the Classical music tradition.

Music boxes tend to have a mechanical organ, an organ that is self-playing, rather than played by a musician. For example, the barrel organ is activated either by a person turning a crank, or by clockwork driven by weights or springs.

Usually, mechanical organs are pipe organs although some instruments were built using reeds similar to those found in a harmonium. Since the 1950s, some instruments have been built using electronics to generate the sound, though still operated by mechanical or pneumatic means.

Originally, the music for mechanical organs was stored by pins on a large barrel. Such instruments were called barrel organs. Such organs only have a very limited repertoire, both in the number of musical selections that could be stored, and the length of tune that could be accommodated. Reference: Wikipedia