Moonsound is the name of the cartridge that includes the Yahama OPL4 soundchip. The OPL4 has 2 part:
FM synthesizer (OPL3) and PCM synthesizer (used by PC's computers and known as Wave Table Syntesis.

FM

- Upto eighteen 2-Operator FM channels or 15 FM channels with 5 drum sounds.
- Upto six 4-Operator FM channels (together with an other six 2-Operator channels.
- 8 different waveforms.
- Possibility to specify right,left or both for each channel.

PCM

- Upto 24 waves simultaneously! (24 channels)
- Replayfrequency of 44.1 kHz
- 8, 12 or 16 wavedata
- Stereo signal in 16 positions for each channel