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# Yamaha YM2612
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one of two chips that powered the Sega Genesis. it is a six-channel, four-operator FM synthesizer. channel #6 can be turned into 8-bit PCM player, that via software mixing, thanks to Z80 sound CPU, can play more than one channel of straight-shot samples at once.
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as of Furnace 0.6pre5, Furnace offers DualPCM, a Z80 driver that splits channel 6 into two individual PCM channels with variable pitch. using the console's Z80 processor, these are mixed together in software and streamed to channel 6 in PCM mode with a mix rate of 13750 Hz. because this generates a stream of data, exported VGM files will be very large.
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# effects
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- `10xy` : **set LFO parameters.**
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- `x` toggles the LFO.
- `y` sets its speed.
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- `11xx` : **set feedback of channel.**
- `12xx` : **set operator 1 level.**
- `13xx` : **set operator 2 level.**
- `14xx` : **set operator 3 level.**
- `15xx` : **set operator 4 level.**
- `16xy` : **set multiplier of operator.**
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- `x` is the operator (1-4).
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- `y` is the multiplier.
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- `17xx` : **enable PCM channel.**
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- this only works on channel 6.
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- `18xx` : **toggle extended channel 3 mode.**
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- 0 disables it and 1 enables it.
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- only in extended channel 3 chip.
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- `19xx` : **set attack of all operators.**
- `1Axx` : **set attack of operator 1.**
- `1Bxx` : **set attack of operator 2.**
- `1Cxx` : **set attack of operator 3.**
- `1Dxx` : **set attack of operator 4.**
- `30xx` : **enable envelope hard reset.**
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- this works by inserting a quick release and tiny delay before a new note.
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- `50xy` : **set AM of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` determines whether AM is on.
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- `51xy` : **set SL of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` is the value.
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- `52xy` : **set RR of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` is the value.
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- `53xy` : **set DT of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` is the value:
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- `0` : -3
- `1` : -2
- `2` : -1
- `3` : 0
- `4` : 1
- `5` : 2
- `6` : 3
- `7` : -0
- `54xy` : **set RS of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` is the value.
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- `55xy` : **set SSG-EG of operator.**
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- `x` is the operator (1-4). a value of 0 means "all operators".
- `y` is the value (0-8).
- values between 0 and 7 set SSG-EG.
- value 8 disables it.
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- `56xx` : **set DR of all operators.**
- `57xx` : **set DR of operator 1.**
- `58xx` : **set DR of operator 2.**
- `59xx` : **set DR of operator 3.**
- `5Axx` : **set DR of operator 4.**
- `5Bxx` : **set D2R/SR of all operators.**
- `5Cxx` : **set D2R/SR of operator 1.**
- `5Dxx` : **set D2R/SR of operator 2.**
- `5Exx` : **set D2R/SR of operator 3.**
- `5Fxx` : **set D2R/SR of operator 4.**
