What game?

FWIW The Sound Blaster Pro's Win3.1 drivers ship a Voyetra SuperSAPI FM synth driver which is very dfiferent. I hope it's not that.

I think that the OP may have selected the original SBPro in those games in question. That one has a dual OPL2 chip configuration and whose routines for stereo separation aren't compatible with a single OPL3 chip which will output mono on both left and right speakers.

leileilol wrote on 2022-12-08, 00:25:

What game?

FWIW The Sound Blaster Pro's Win3.1 drivers ship a Voyetra SuperSAPI FM synth driver which is very dfiferent. I hope it's not that.

An old vertical shooting game whose executable goes by the name DUCK. I originally had it on an old game CD of mine that was eventually discarded as it was no longer readable anymore (the CD had a lot of stuffs and I did not have any good means to properly back them up back then), but was able to find it again on a Russian site recently. It's been more than two decades since I last played it. My PC at that time had an ESS 688 which was also SB Pro compatible, and the game's music on YMF718 sounded just like how it used to be.

I did not immediately mention it before as the game was rather uncommon, but the phenomenon I noticed seems to happen on many games that use standard MIDI rather than specialized formats (such as IMF, SND) for music.

Gmlb256 wrote on 2022-12-08, 00:51:

I think that the OP may have selected the original SBPro in those games in question. That one has a dual OPL2 chip configuration and whose routines for stereo separation aren't compatible with a single OPL3 chip which will output mono on both left and right speakers.

The game I'm referring to does not have options for SB Pro or SB 16 (it auto-detects). But I know some other DOS games that do. For these games (that also use MIDI for music), choosing SB Pro and SB 16 will lead to different sounding music just like this case, though the games may not really bar you from using SB16 option even with only a SBPro compatible card.

You may be right about the stereo/mono difference, as from what I could hear, aside from differences in instruments, some notes previously near-inaudible with SB Pro can be heard clearly with SB 16, so it's probably only one channel being actually outputted through the OPL3 when the game operates in SB Pro mode (such as with YMF718).

Since all the cards I have, be it SBPro or SB16, use OPL3 (YMF262/289), I won't be able to dig deeper regarding differences between dual-OPL2 and OPL3, and I've no real idea which "version" is the one that the MIDI was supposed to be. Personally speaking, in some cases the SBPro one sounded better, while in other cases, the SB16 one.

LATE EDIT: Guess the game does differentiate between different SB revisions. Further digging of the game files led me to some MIDI driver (DRV) files for different SB revisions (original, Pro, 16, etc.). So the game was indeed using different drivers depending on the card's Sound Blaster capability.

LATE EDIT 2: The game had MIDI drivers for SB2.0, SBPro, SBPro2.0 and SB16. I experimented with substituting the SB16 driver with other ones and turned out the difference was indeed caused by the driver being used. When I used the SBPro MIDI driver in place of the SB16 one, the music now sounds just like how it was with a ESS688/YMF718.