Thanks for the replies. Most of my old games that I have problems with are Windows-based though. I need to get better taste in games.
Update on the situation
at VOGONS.
Basically, bad MIDI playback is a known issue with Virtual PC. The solution is to use a software synthesiser as the MIDI output device instead of the default. I'm using
Wingroove 0.A4 Beta, though I've heard that it's not the best for games. At least it's entertaining and doesn't sound like someone raping my ears with a 2x4.
In Windows 98 setting up the softsynth of choice is Start > Settings > Control Panel > Multimedia > MIDI.
More information
here, although that's not written for VPC or Win9x.
VMware Player seems to be okay with MIDI, but there are other reasons I'm not using it.