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The Yamaha YM3812 also known as the OPL2 is a sound chip (i.e. integrated circuit) created by Yamaha Corporation and famous for its wide use in IBM PC-based sound cards such as the AdLib and Sound Blaster.
The circuit has 244 different write-only registers. It can produce 25 independent sine waves which may also be modified to mimic triangular wave (sine waves with the negative part turned upward) and sawtooth waves (1/4 sine waves upward only with silent sections inbetween. This odd way of producing waveforms give the YM3812 a characteristic sound. Each wave generator has its own amplitude modulator.
