it's well known that GS means "sound canvas" essentially.

However, what's probably less well known is that XG is tied specifically to Yamaha's Advanced Wave Memory 2 synthesis engine.

My evidence of this is the TG300 midi data reference.

The TG300, as we all know has two modes. mode a, and mode b. Mode b is an attempt at playback of GS midi correctly down the the sysex.

Now it turns out the TG300 has variation effect, and not only that, it has the sysex to change part parmeters that XG devices have!

So it seems the TG300 was a prototype for XG, and it is known to use AWM2.

While some non yamaha stuff has XgLite, the only products i've found that were not Yamaha, but support XG (Korg stuff) simply did it by adding in a plugin board in the factory made by Yamaha.

XG was designed to leverage the capabilities of the AWM2 synthesis engine inside of MIDI, as well as the effect DSPs.