Yamaha XG
Yamaha's 1994 answer to Roland GS: an even bigger superset of General MIDI with hundreds of extra voices and several effect blocks.
XG launched with the MU80 tone generator and follows the same idea as its rival: the GM sounds stay where they are, and everything new sits behind bank select. Yamaha simply went bigger. The spec demands more polyphony, far more voice variations and, alongside reverb and chorus, a third effect block for anything from distortion to rotary speaker. Almost every parameter is reachable via NRPN.
XG turned up on daughterboards, sound cards and Yamaha's own keyboards through the late 1990s. But once game developers moved to recorded audio on CD, and later to compressed files, the GS-versus-XG format war ended without a winner, mainly because the audience had left the building.