First post, by raymangold22
Since this topic hasn't been covered a whole lot, let me start at the basics (advanced apologies to those who already know this). I'll also include some quick sound samples.
When Yamha released their OPL3 Chip (YMF262), it was used in a lot of cards... probably the most popular being the SoundBlaster 16.
Well it wasn't long before other companies (ESS technology, Crystal Semiconductor, OPTi, Creative LABS etc) caught on and decided to make their own OPL3 implementation: this both allowed a larger profit as they didn't have to pay Yamaha for the YMF262 chips, and also gave them the ability to tweak the FM behaviour to their heart's content.
In many cases, these implementations are poorly documented, and are shoved behind the scene by YMF262 (all of those boring OPL3 emulators try to copy YMF262 as if it's the only OPL3 chip)... but in fact, I couldn't imagine OPL3 without them!
#1 Crystal FM Synthesis (as found on Crystal 4236B aka CS4236: CX4235 & CS4280 are corrupted).
Crystal is notable for its distinct noise generator (very distinct hihats, cymbal crashses, subtle octaved frequency shifting on toms -- similar to Sytrus, and "electronic splashes"), higher treble, and faster envelopes. It's my personal favourite OPL3.
#2 ESS ESFM (as found on ESS SOLO-1). ESFM is probably one of the most radically different OPL3 implementations in that it can be subtle. Sometimes it can sound very close to YMF262 (moreso than crystal), but other times, completely different. Because of its use of custom FM instruments under windows, it'll always sound different than YMF262 and CS4236, but there are mixed results in adlib tracker 2. Its major characteristics include slower vibrato, discreet portmanteau, balanced treble/bass, deep toms, and an odd fuzzing distortion on some custom patches.
#3 Dual OPL3: a combination of CS4236 & YMF262 (via SB16) running at once. Humorously, when I plugged my SB16 into my 233 P1 IBM, it couldn't help itself from playing along with the Crystal FM! Because of this, both soundcards will respond to MIDI information at the same time...
This can only be done with certain sound cards: so don't get too excited.
Stuff in dual OPL3 sounds fantastic! Crystal gets all the highs and lends its unique noise generator for drum sounds, and SB16 gets all the deep bassy lows.
ESFM playing Phandral's Spiral: http://www.youtube.com/watch?v=yBYL0Nq38cc
ESFM playing wheelchair (notice the fuzzing distortion): http://www.youtube.com/watch?v=0yKHGPGtI3s
Dual OPL3 gubble 2 menu (notice the phasing between the two chips as Crystal isn't 100% like YMF262): http://www.youtube.com/watch?v=O9mA71PTReM
Dual OPL3's nice chorussed metallic sound: http://www.youtube.com/watch?v=mk-7u0ZDUFw
Crystal's discreet hihats and cymbal crashes: http://www.youtube.com/watch?v=3EZLMAADXuc
Well that's all folks. If there's interest I can get deeper into the subject, otherwise I'll leave it at that.