# Yamaha OPL

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!

essentially a downgraded version of Yamaha's other FM chips, with only 2 operators per channel.
however, it also had a [drums mode](opll.md), and later chips in the series added more waveforms (than just the typical sine) and even a 4-operator mode.

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.

Y8950 is essentially the same chip, but with one additional channel for ADPCM sample playback, behaving in a similar way as the one found in YM2608.

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.
later Creative would borrow the chip to make the Sound Blaster, and totally destroyed AdLib's dominance.

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 and some other things.

the OPL4 (Yamaha YMF278) retains the FM block from OPL3, but adds 24 sample channels on top! samples are 44100 Hz, can be between 8, 12 or 16-bit, stereo (with 16 different levels) and can read PCM data from ROM or SRAM (up to 4 MB).

afterwards everyone moved to Windows and software mixed PCM streaming...

## effects

- `10xx`: **set AM depth.** the following values are accepted:
  - `0`: 1dB (shallow)
  - `1`: 4.8dB (deep)
  - this effect applies to all channels.
- `11xx`: **set feedback of channel.**
- `12xx`: **set operator 1 level.**
- `13xx`: **set operator 2 level.**
- `14xx`: **set operator 3 level.**
  - only in 4-op mode (OPL3 and OPL4).
- `15xx`: **set operator 4 level.**
  - only in 4-op mode (OPL3 and OPL4).
- `16xy`: **set multiplier of operator.**
  - `x` is the operator (1-4; last 2 operators only in 4-op mode).
  - `y` is the new MULT value..
- `17xx`: **set vibrato depth.**
  - `0`: normal
  - `1`: double
  - this effect applies to all channels.
- `18xx`: **toggle drums mode.**
  - `0` disables it and `1` enables it.
  - only in drums 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.**
  - only in 4-op mode (OPL3).
- `1Dxx`: **set attack of operator 4.**
  - only in 4-op mode (OPL3).
- `2Axy`: **set waveform of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` is the value.
  - only in OPL2 or higher.
- `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 from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` determines whether AM is on.
- `51xy`: **set SL of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` is the value.
- `52xy`: **set RR of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` is the value.
- `53xy`: **set VIB of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` determines whether VIB is on.
- `54xy`: **set KSL of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` is the value.
- `55xy`: **set SUS of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` determines whether SUS is on.
- `56xx`: **set DR of all operators.**
- `57xx`: **set DR of operator 1.**
- `58xx`: **set DR of operator 2.**
- `59xx`: **set DR of operator 3.**
  - only in 4-op mode (OPL3).
- `5Axx`: **set DR of operator 4.**
  - only in 4-op mode (OPL3).
- `5Bxy`: **set KSR of operator.**
  - `x` is the operator from 1 to 4; the last 2 operators only work in 4-op mode. a value of `0` means "all operators".
  - `y` determines whether KSR is on.

## info

these chips use the [FM (OPL)](../4-instrument/fm-opl.md) instrument editor.
Y8950 ADPCM uses [Generic Sample](../4-instrument/sample.md) and [ADPCM-B](../4-instrument/adpcm-b.md) instrument editors.
OPL4 PCM uses the [MultiPCM](../4-instrument/multipcm.md) instrument editor.

when two channels are joined for 4-op mode, the channel bar will show `4OP` on a bracket tying them together.

sample lengths on the Y8950 are padded to multiples of 512 samples. ADPCM samples ignore loop points; they may only be loop over the entire sample.

OPL4 maximum sample length is 65535.

## chip config

the following options are available in the Chip Manager window:

- **Clock rate**: sets the rate at which the chip will run.

additionally, in OPL3:

- **Chip type**: sets the chip model. OPL3-L uses resampling.
- **Compatible panning**: for compatibility with old Furnace.

additionally, in OPL4:

- **RAM Size**: sets the RAM size for sample storage.
