Success!!! Thanks so much for all the help and encouragement. I can now play Wing Commander with my MT-32 via the Music Quest PC MIDI Card. I got past the pre-intro, fireworks (where it usually crashed), through the intro, went to the two screens on the Tiger's Claw (kind of a small ship, no?), a mission briefing, a combat mission escorting a Drayman, a debriefing, and a bronze star award ceremony... all with no freezes!
Funny thing is, I think I prefer the Adlib music and sound effects during actual combat, ha ha ha... But the rest of the music is nicer and I have a bunch of other games to try with the MT-32... finally, after 30 years... (I wanted this setup back when I was 15, but the MT-32 was NOT in my childhood budget).