I don't know if it's done on a real chip or not, but that's FM synthesis, like produced by the http://en.wikipedia.org/wiki/Yamaha_YM2612 http://en.wikipedia.or

I don't know if it's done on a real chip or not, but that's FM synthesis, like produced by the http://en.wikipedia.org/wiki/Yamaha_YM2612 http://en.wikipedia.org/wiki/Yamaha_YM2612 in SEGA machines.