# Yamaha YM2612

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.

# effects

- `10xy`: set LFO parameters.
  - `x` toggles the LFO.
  - `y` sets its speed.
- `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.
  - `x` is the operator (1-4).
  - `y` is the multiplier.
- `17xx`: enable PCM channel.
  - this only works on channel 6.
- `18xx`: toggle extended channel 3 mode.
  - 0 disables it and 1 enables it.
  - only in extended channel 3 chip.
- `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.
  - this works by inserting a quick release and tiny delay before a new note.
- `50xy`: set AM of operator.
  - `x` is the operator (1-4). a value of 0 means "all operators".
  - `y` determines whether AM is on.
- `51xy` set SL of operator.
  - `x` is the operator (1-4). a value of 0 means "all operators".
  - `y` is the value.
- `52xy` set RR of operator.
  - `x` is the operator (1-4). a value of 0 means "all operators".
  - `y` is the value.
- `53xy` set DT of operator.
  - `x` is the operator (1-4). a value of 0 means "all operators".
  - `y` is the value:
    - 0: -3
    - 1: -2
    - 2: -1
    - 3: 0
    - 4: 1
    - 5: 2
    - 6: 3
    - 7: -0
- `54xy` set RS of operator.
  - `x` is the operator (1-4). a value of 0 means "all operators".
  - `y` is the value.
- `55xy` set SSG-EG of operator.
  - `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.
- `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.
