Roland GS, or just GS, sometimes expanded as General Standard or General Sound, is an extension of General MIDI specification. It requires that all GS-compatible equipment must meet a certain set of features and it documents interpretations of some MIDI commands and bytes sequences, thus defining more instrument tones, more controllers for sound effects, etc.
GS takes into account some of the criticism of simplicity of original General MIDI standard, while retaining full forward compatibility and even some backward compatibility. GS defines 98 additional tone instruments, 15 more percussion instruments, 8 more drum kits, 3 effects (reverb/chorus/variation) and some other features, thus adding more sounds to the MIDI world. Roland also gave users their own MIDI file player, called SB-55 Sound Brush.
The Roland SC-55, the first synthesizer to support the General MIDI standard, also supports the GS standard.
Organizations from around the world believed that General MIDI could be made more versatile, so Roland created the GS standard. It is still an extension of the GM specification, meaning it can provide many extra controllers and sounds while still keeping to the sound map and obeying all the protocols of GM. This means the user of the Roland GS standard will also be able to play back any song designed for General MIDI, while still giving the option to add more effects and sounds. Composers can alter sounds with the Roland GS professionally using a set of Roland exclusive system features that allow the reconfiguration and customization to be achieved. The GS extensions were first introduced and implemented on Roland Sound Canvas series modules, starting with the Roland SC-55 in 1991. The first model supported 317 instruments, 16 simultaneous melodic voices, 8 percussion voices and a compatibility mode for Roland MT-32 (although it only emulated it and lacked programmability of original MT-32) and gained explosive popularity.
In addition to the Sound Canvas series, Roland also provided GS compatibility in its own professional lineup through the JV-30 keyboard and the VE-GS1 expansion board for other JV-series instruments. In addition, GS compatibility is provided in the GM2 specification which Roland helped to create and actively supports.
The comparison of GS to General MIDI is still there as the program in every individual bank will align with the original 128 in GM's instrument patch map. The Sound Canvas used additional pair of controllers, cc#0 and cc#32, to specify up to 16384 (128*128) 'variations' of each melodic sound defined by General MIDI. Typically, cc#32 (Bank Select LSB) was used to select a family (i.e. 1 - SC-55, 2 - SC-88 etc.) then cc#0 (Bank Select MSB) was used to set a particular variation bank.
MIDI channel 10 is used for drums by default like in General MIDI, but they are accessible on any channel through the use of SysEx. Only 2 different drum kits can be used at a time. There are 15 different kits in total:
There were 16 additional drum notes that span Drum Kits 1 to 49:
Additional controller events included in SC-55 and SC-88 were:
There were messages that allowed the user to turn the GS mode on/off, to set effects processor parameters, to change EG envelopes etc.
Beginning in 1991, Roland introduced GS support in the majority of its MIDI products.