hifidelitygaming wrote:

was it just a reverb/chorus type enhancement (outputting only stereo) or did it actually enable some kind of surround sound output?

which cards was it compatible with, adlib gold only?

Two-channel digital delay (echo)

Yamaha's YM7128B chip is used on the Ad Lib "surround module," which is only compatible with the Gold card. You can find the datasheet for this chip in the thread here, if you're interested in more detail.

Did games have to have some special support for the surround enhancements, or was it always on during all adlib soundtracks/effects?

Programmed support isn't a requirement. Using the Gold's mixer panel, the surround option can be enabled or disabled, the level adjusted, and any of the following eight presets selected:

Recital Hall
Concert Hall
Chapel
Jazz Club
Movie Theater
Stadium
Cavern
Deep Space

I'm not sure if the Dune tracks were programmed to use just these presets, or if they're using something custom. The control register in question doesn't appear to have ever been fully documented besides...

Is it only those eight presets? Ie - the specifics of reverb and delay aren't adjustable, it's just a selection of those fixed environments... are environments outside those eight possible based on the hardware?

Were those presets selected by the software in games supporting the surround module? ie - soundtrack A might use Recital Hall and soundtrack B (or sound effectS) might use Jazz Club?

It sounds like Dune or KGB are the 'killer' apps for this card, so if anything used it they probably did. It doens't sound like there were other standout games for music... (meaning above general OPL2/3 ability also on soundblaster)