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46 lines
2 KiB
Markdown
46 lines
2 KiB
Markdown
# Yamaha OPL
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a series of FM sound chips which were very popular in DOS land. it was so popular that even Yamaha made a logo for it!
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essentially a downgraded version of Yamaha's other FM chips, with only 2 operators per channel.
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however, it also had a drums mode, and later chips in the series added more waveforms (than just the typical sine) and even a 4-operator mode.
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the original OPL (Yamaha YM3526) was present as an expansion for the Commodore 64 and MSX computers (erm, a variant of it). it only had 9 two-operator channels and drums mode.
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its successor, the OPL2 (Yamaha YM3812), added 3 more waveforms and was one of the more popular chips because it was present on the AdLib card for PC.
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later Creative would borrow the chip to make the Sound Blaster, and totally destroyed AdLib's dominance.
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the OPL3 (Yamaha YMF262) added 9 more channels, 4 more waveforms, rudimentary 4-operator mode (pairing up to 12 channels to make up to six 4-operator channels), quadraphonic output (sadly Furnace only supports stereo) and some other things.
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afterwards everyone moved to Windows and software mixed PCM streaming...
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# effects
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- 10xx: set AM depth. the following values are accepted:
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- 0: 1dB (shallow)
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- 1: 4.8dB (deep)
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- this effect applies to all channels.
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- `11xx`: set feedback of channel.
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- `12xx`: set operator 1 level.
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- `13xx`: set operator 2 level.
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- `14xx`: set operator 3 level.
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- only in 4-op mode (OPL3).
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- `15xx`: set operator 4 level.
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- only in 4-op mode (OPL3).
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- `16xy`: set multiplier of operator.
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- `x` is the operator (1-4; last 2 operators only in 4-op mode).
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- `y` is the mutliplier.
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- 17xx: set vibrato depth. the following values are accepted:
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- 0: normal
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- 1: double
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- this effect applies to all channels.
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- `18xx`: toggle drums mode.
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- 0 disables it and 1 enables it.
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- only in drums system.
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- `19xx`: set attack of all operators.
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- `1Axx`: set attack of operator 1.
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- `1Bxx`: set attack of operator 2.
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- `1Cxx`: set attack of operator 3.
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- only in 4-op mode (OPL3).
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- `1Dxx`: set attack of operator 4.
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- only in 4-op mode (OPL3).
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