FM Synthesis
Frequency modulation music
FM synthesis creates complex timbres by modulating one oscillator's frequency with another, powering the Yamaha sound chips in computers and consoles.
Overview
FM (frequency modulation) synthesis creates sound by using one oscillator (the modulator) to modulate another’s frequency (the carrier). The result: complex harmonics from simple sine waves. Yamaha licensed John Chowning’s research and built it into chips like the YM2612 (Mega Drive) and OPL series (PC). FM’s metallic, bell-like timbres defined an era of game audio.
Fast facts
- Inventor: John Chowning (Stanford, 1967-1973).
- Licensee: Yamaha (1975).
- Gaming chips: YM2612 (Mega Drive), OPL2/3 (AdLib/Sound Blaster).
- Operators: carrier and modulator oscillators.
- Sound character: metallic, bell-like, complex.
How it works
FM synthesis basics:
- Carrier: oscillator that produces the sound.
- Modulator: oscillator that changes carrier’s frequency.
- Algorithms: different operator configurations.
- Ratios: modulator frequency ratio determines timbre.
Platform implementations
Where FM synthesis appeared:
- Mega Drive/Genesis: YM2612 chip.
- PC AdLib/Sound Blaster: OPL2/OPL3 chips.
- MSX: Yamaha chips in various models.
- Arcade: numerous Yamaha-equipped boards.