Platform - OPLL (FM)
Tunes that use Yamaha OPL/OPL2/OPL3/OPLL synthesis. OPL is an acronym for FM Operator Type-L.
It all started with the YM3526, aka OPL (FM Operator Type-L), which is a sound chip developed by Yamaha as a low-cost nine channel, two operator FM synthesis chip. It was notably used in a Commodore 64 expansion, the Sound Expander, as well as several Arcade games, such as Bubble Bobble.
A very closely related chip is the Y8950, or MSX-AUDIO, which was used as an MSX expansion. It is essentially a YM3526 with ADPCM recording and playback capability.
(info taken from Wikipedia)