General MIDI 1
The General MIDI 1 is a set of recommendations which seeks to provide a way to go beyond the limitations of proprietary designs, and standardize the MIDI capabilities of sound generating devices. Sound generating devices and music files that meets the General MIDI 1 standard bears the General MIDI logo. Music files bearing the General MIDI logo can be played back using any General MIDI sound generating unit to produce essentially the same musical preformance.
General MIDI 2
The General MIDI 2 is a set of recommended specifications that provide detailed definitions for functionality such as sound editing and effects that had not been defined in the General MIDI 1, and extend the sound map to allow a higher degree of performance expression and compatibility. Since the General MIDI 2 is compatible with the General MIDI 1, it is capable of reliabily playing back music files bearing the General MIDI logo.
GS Format
The GS Format is Roland's set of specifications for standardizing the performance of sound generating devices. In addition to including support for everything defined by the General MIDI 1, the highly compatible GS Format additionally offers an expanded number of sounds, provides for the editing of sounds, and spells out many details for a wide range of extra features, including effects such as reverb and chorus. Designed with the future in mind, the GS Format can readily include new sounds and support new hardware features when they arrive.