The OPL-3 FM 128M is - as its name suggests - a soundfont based on the OPL-3 (YMF262) of Yamaha, an audio chip close to the Sega Megadrive/Genesis but having 18 channels instead of 6.

It is considered as "The Ultimate Megadrive Soundfont", but the name is already taken by another soundfont: the GenesiSF soundfont!