An addition to the original MIDI specification that allows for consistent playback on any instrument that is GM compatible. Achieved by requiring that groups of sounds have very specific locations (a piano sound on one synthesizer will have the same location on another,) that all instruments have 24-voice polyphony, and that certain continuous controllers are similarly defined. In theory, music sequenced for General MIDI should play back on any other GM instruments with the similar type of sound on the same MIDI track with any volume and pan information also being executed as written.
(See MIDI)