YM2612 Overview
“The Yamaha 2612 Frequency Modulation (FM) sound synthesis IC
resembles the Yamaha 2151 (used in Sega’s coin-op machines) and the
chips used in Yamaha’s synthesisers.
It is famously known as the Sega Megadrive’s voice.
An FM channel is capable of expressing, with a high degree of realism, a
single note in almost any instrument’s voice. Chords are generally created
by using multiple FM channels.
The standard FM channels each have a single overall frequency and data
for how to turn this frequency into the complex final wave form (the
voice). This conversion process uses four dedicated channel components
called ‘operators’, each possessing a frequency (a variant of the overall
frequency), an envelope, and the capability to modulate its input using
the frequency and envelope. The operator frequencies are offsets of
integral multiples of the overall frequency.
There are 6 FM channels. Channels 3 and 6, have the capability to use a
totally separate frequency for each operator rather than offsets of integral
multiples (ch3 special mode). This works well for sound effects and
experimental instruments.
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