Yamaha · 1986 · 1980s · 9 voices
The YM2413 was Yamaha's budget FM chip: nine two-operator channels, fifteen instruments burned into silicon and room for exactly one of your own. It gave the Japanese Master System and the MSX their FM voice.
The YM2413, usually called the OPLL, was Yamaha's answer to a simple commercial question: how cheap can FM synthesis be made? First produced in 1986, it is a stripped-down relative of the OPL family found in AdLib and Sound Blaster cards. It offers nine concurrent FM channels with two operators each, and a rhythm mode that trades the last three melodic channels for five percussion sounds. To get the cost down Yamaha removed most of the internal registers, reduced the available waveforms to two and multiplexed the channels in time rather than mixing them simultaneously. The most consequential cut was to the instruments themselves: fifteen voice settings are hard-coded into the chip, and only one user-defined instrument can be active at a time. Composers therefore worked with a fixed palette — piano, violin, guitar, trumpet, organ and the rest — plus one custom sound they had to choose carefully. In games the chip is best known from Sega's FM Sound Unit for the Mark III, whose circuitry was built into the Japanese Master System, so many Master System titles carry a second, richer FM soundtrack that Western owners never heard. On the MSX it became the MSX-MUSIC standard, built into select MSX2 and MSX2+ machines and every MSX turbo R. It also turned up in Yamaha's own home keyboards and on arcade boards including Atari Games' Rampart.