Orchestrion is a generic name for a machine that plays music and is designed to sound like an orchestra or band. Orchestrions may be operated by means of a large pinned cylinder or by a music roll and less commonly book music. The sound is usually produced by pipes, though they will be voiced differently from those found in a pipe organ, as well as percussion instruments. Many orchestrions contain a piano as well. At the Musical Museum in Brentford, examples may be seen and heard of several of the instrument types described below.

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 who plays a barrel organ is known as an organ grinder.