NewRisingSun wrote:One known reason for this particular game slowing down is having selected Roland MT-32 music in the INSTALL program without having an original Roland MIDI interface.
I can second that.
A chance acquisition of a 486DX33 started my re-delving into the world of retro-computing after the better part of a decade. I soon realized that my partner's Roland digital piano had MIDI connectivity and GM (and indeed GS) support, so could be seen as a somewhat large SC-55 with built-in speakers and too many black and white keys. Of course, MT-32 isn't GM, but close enough to be worth a try. I'd never used MIDI with games before, so naievely hooked it up to my SBPro2-compatible Aztech 2316A-based card and assumed it would work. It did with some titles (eg. Colonization and Tyrian), but not with Ultima 6 - no music, and - relevantly - huge slowdown. No problems at all if I selected AdLib or PC Speaker.
The issue was lack of intelligent mode on the MPU-401-clone on the sound card. Loadin the SoftMPU TSR in Autoexec.bat solved it conveniently (and by loading it high it didn't even cost me any conventional memory). Later I got a real MT-32 and it works just as well, including the little messages on the screen.
So: not sure if that is your issue, but if you have an external MIDI device, use SoftMPU. If not, don't select MT-32 as sound. If you don't have MT-32 selected, you have some other problem.