What is Barrel organ?

A barrel organ is a French mechanical musical instrument consisting of bellows and one or more ranks of pipes housed in a case, usually of wood, and often highly decorated. The basic principle is the same as a traditional pipe organ, but rather than being played by an organist, the barrel organ is activated either by a person turning a crank, or by clockwork driven by weights or springs. The pieces of music are encoded onto wooden barrels , which are analogous to the keyboard of the traditional pipe organ. A person which plays a barrel organ is known as an organ grinder.