This doesn't answer your question specifically, but it may be of interest:

http://www.descent2.com/goodies/music/

Been there.

But speaking of which, the FM MIDI soundtracks they have up there for Descent 1 and 2.....just how are you supposed to play those? You can't just play it on a FM synth sound card with a Windows MIDI player because any MIDI file played in Windows will just be played back as General MIDI...and the drum tracks, for one, aren't on the correct General MIDI standard channel. So I'm a little confused as to how one is supposed to listen to those...

on a Windows FM midi driver. Of course it still won't be the same, but since the site came from a time when wavetable MIDI wasn't widely used that's thrown up there anyway

No, that doesn't work. Even a Windows FM MIDI driver still goes under the assumption that the MIDI file is General MIDI and plays it as such. So it wouldn't play any better on a Windows FM driver than it would on a wavetable one. I've tried it. The drums are just pianos because it's using the wrong channel. And all the instruments sound horrible...even in FM. As if they're the wrong notes.

It's as if these MIDI files will only play correctly within the game itself.

I had a looksie at the "D1 Full Version for FM" in my MIDI sequencer... definitely *strange* looking to say the least.

The MIDI files appear to be type 1 and are not tagged "Mark for Microsoft Media Player", yet only the first two tracks are actually assigned MIDI channel numbers (channel 1).