1.) FM Synthesis
The YM3812, known more colloquially as the OPL2, is an integrated circuit created by Yamaha. Specifically, it is a programmable sound generator which creates audio waveforms using FM synthesis. The YM3812 was used in many arcade games, but was especially popular on home computer sound cards from the late 1990s to the mid-1990s, particularly in the Ad Lib Music Synthesizer Card and Sound Blaster lines. The YM3812 outputs mono audio, but some sound cards, like the Sound Blaster Pro, linked two chips together for stereo output.
Yamaha created an entire family of chips designated OPL, which is short for FM Operator Type-L. The YM3812 is the second chip in the line and is fully backward compatible to its predecessor, the YM3526, or OPL. In fact, the two chips are identical except for the additional 3 waveforms of the YM3812. Another near identical chip is the YM2413 or OPLL, a slimmed down version of the YM3812. The chip's successor is the YMF262 or OPL3, which was found on many 16-bit sound cards.
The YM3812 has two modes:
- In melody mode, it produces 9 individual audio channels, each made of two oscillators, connected through either FM or additive synthesis.
- In rhythm mode, it produces 11 channels: Channels 1 to 6 are for melodies and channels 7 to 11 for bass drum, snare drum, tom, crash cymbal and hi-hat. Channel 7 still uses 2 oscillators, but channels 8 to 11 use only 1 oscillator each and are accompanied by channel-specific noise.
Drums are still possible in melody mode, and some arrangers preferred more melody channels and less rhythm channels.
Each oscillator can produce sine waves which may also be modified into 3 other waveforms – the negative part of the sine can be muted or inverted, and pseudo sawtooth waves (1/4 sine waves upward only with silent sections in between) can also be produced. Each oscillator has its own ADSR envelope generator, and vibrato and tremolo switches. All channels must share the same vibrato and tremolo depths and rates. A very few drivers, most popularly Loudness, featured much more flexible software vibratos and tremolos.
The OPL2 is able to play unsigned 6-bit PCM samples on one channel's output level register.
Some versions sound a bit different, although they are not identified yet. One VGMPF contributor clearly remembers that the rhythmic notes at 0:07 of Dungo - Jill Goes Underground (DOS) sounded 1½ octaves lower (more in tune, too) on whatever Sound Blaster compatible he had by late 1994. He still has exactly the same copy of the game, but on his Sound Blaster 16 CT1740, they sound high (less in tune).
The YM3812 can be found on the following devices:
|1987-??-??||Ad Lib||Ad Lib Music Synthesizer Card||1|
|1990-??-??||Creative||Sound Blaster 1.5||1|
|1990-??-??||Media Vision||Thunder Board||1|
|1991-10-??||Creative||Sound Blaster 2.0||1|
|1991-??-??||Creative||Sound Blaster Pro||2|
|1991-??-??||Covox||Sound Master Plus||1|
|1991-??-??||Media Vision||Pro AudioSpectrum||2|
|1992-05-??||Media Vision||Pro AudioSpectrum 16||?|
|199?-??-??||Creative||Sound Blaster MCV||1|
|199?-??-??||Covox||Sound Master II||1|
|199?-??-??||Media Vision||Pro AudioSpectrum 16 Basic||?|
|199?-??-??||Media Vision||Pro AudioSpectrum 16 Studio||?|
This list is meant to be in chronological order, but many release dates are missing.
Dozens of arcade games used the YM3812.
- This list is incomplete.
|Manual||Download - (info)|
The YM3812 is emulated by DOSBox, MAME, and AdPlug. However, samples sound too raspy in DOSBox 0.74.