First thing I'd think of to do is re-run the software install in case it ran a speed calibration and saved a value somewhere. .. ... well that's after being 200% sure I didn't knock anything when I was inside the case.

I removed the installed files and installed the sound card drivers (as well as scrubbing autoexec.bat / config.sys) but am still having the same issue. I tested the Dreamblaster on another machine and it is working just fine. I'm worndering if it could be an issue with interrupts, but would installing an Overdrive change anything with DMA/interrupts?

After some additional troubleshooting I've narrowed the issue down to the Wavetable header/Dreamblaster. Without anything connected to it and all games using Soundblaster for midi playback there aren't any issues, but when I connect the Dreamblaster and change the MIDI settings to General Midi the instrumentation is off. I've tested the Dreamblaster playing midi when connected via USB and it plays just fine, this also worked just fine before installing the Overdrive processor. Has anyone heard of an issue like this?

Just posting this in case it helps anyone else, after messing with IRQs and interrupts for some time (the recommendation after getting a WSS Initialization error in the readme), I went back to the drivers again and gave the Unisound driver a shot. With Unisound I had no more initialization errors and midi is working great, both with the cache disabled in Sierra games and in games like Daggerfall and Mechwarrior 2.

You shouldn't have to have cache disabled, especially in MechWarrior 2. I played that with a much faster CPU back in the day.

Ah sorry should have been more specific, I was only disabling the cache on the Sierra games. Mech2 would be a slideshow with the cache disabled 😁