I was having trouble with Space Quest 4. The music was working fine until the first digital sound effect played. After that, the music plays but it's all crazy, but digital sound effects (incl speech) continue to function as normal. I was not having the same problem with SQ3, SQ5 or any other MT-32 enabled game.
My system is a 486 DX2/66, with an ISA SB16 PnP (CT2940) and an MT-32 connected to the SB's gameport with the appropriate cable.
I tried all the fixes, turning off turbo, MoSlo, pre-loading the patches to the MT-32, the various Sierra driver solutions on offer at Quest Studios, and even a replacement sound card, but to no avail.
Surprisingly, I found my solution in a patch that specifically says it is NOT for SQ4. The package at this address is intended to fix "error 29" for SQ1 VGA among others.
This driver will work for the following games:
Police Quest III
Space Quest I Enhanced VGA
Leisure Suit Larry I Enhanced VGA
Leisure Suit Larry V
This file will not work with any other Sierra or Dynamix titles.
For King's Quest V choose the AdLib option and the game will sound
perfect. For Space Quest IV, try slowing the system down when you
start the game by turning off the Turbo button. You can speed it
back up once in the game. If you do not have a Turbo button, you
will need to choose the AdLib option.
Against its advice, I placed the MTBLAST.DRV into my SQ4 folder, added some lines to INSTALL.HLP:
MT-32 / Soundblaster MIDI
Ran the setup utility, picked the new driver, and held my breath.
It runs perfectly. I still have sound effects, speech, and fully functioning MT-32 support (all the custom patches are there!).
So, just thought I'd share this, for any other Quester out there who has tried it all, but still gets nowhere.