Yamaha XG
Yamaha XG is Yamaha's proprietary expansion of the General MIDI standard. It competed with Roland GS.
Although the first XG module was the Yamaha MU80, the baseline for XG support seems to be defined by the less powerful later model, the Yamaha MU50; according to Yamaha, this model is "regarded as the standard of XG tone generators".[1]
See Category:Yamaha XG devices for pages about XG devices. The Yamaha MU series of sound modules is the most notable line of products supporting XG.
Starting with the Yamaha MU100, some XG devices could be expanded with boards from the XG Plug-in System.
See GM–GS–XG quick reference for a list of Control Changes.