Yamaha YM2151

The Yamaha YM2151, also known as the OP-M (FM Operator Type-M) is a sound chip in the YM2100 family. It was Yamaha's first single-chip FM synthesis implementation, created originally for the Yamaha DX series of keyboards. It has eight voices with four operators per voice.

It was also used in arcade games, starting with Atari's Marble Madness, and later being licensed for use by many other companies including Sega, Konami, Capcom, Data East Pinball and Namco, with its heaviest use in the late 1980s, as well as in Sharp X1 and Sharp X68000 home computers.

This chip was used in some Yamaha budget electric pianos, such as the YPR-7/8/9. It is identical to the chip in the FB-01 (YM2164), except that operator 4 of voice 8 can be used to generate noise, all other data is identical.

Finally, the chip was used in the Yamaha SFG-01 and SFG-05 FM Sound Synthesizer Units. These are expansion units for MSX computers and were already built in in some Yamaha MSX machines like the CX5M. It provides the FM synthesizer with stereo output jacks, MIDI ports and a connector for an external keyboard. Note that at least some SFG-05 modules contain an YM2164 chip.