* a distinct rhythm section, which incorporates a noise generator with some of the parts above to provide a few fixed percussion noises.
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=== Operators ===
On an OPL1 or 2, each channel consists of two operators. On an OPL3 it may also consist of four. In either case the basic FM synthesis operation is the same:
The output of one operator is used to modulate the current phase of another. The former is known as the modulator, the latter as the carrier.
In two-operator frequency modulation mode, the output of the carrier, after modulation, is the audio output.
In four-operator mode there are some more complicated options involving routing outputs between operators.
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