I just wanted to give a quick thank you for this project. I bought an MT-32 over 15 years ago without understanding that it wouldn't work with the MPU-401 interface on the SoundBlaster. Real MPU-401 cards have gone for crazy money on eBay even back then, so the module just sat in a box while I tried to get something working. I have an ISA perfboard and an old PIC with some latches. I just didn't really know where to start with the software part, and so it eventually went into the same box.
I ran across HardMPU on eBay, found this thread, and decided what the heck. It works great! This saves me so much time. Prices on MT-32s and SC55s have been on the rise since YouTubers like LGR started talking about them recently (that's what reminded me about my MT-32). With the MPU-401 problem largely solved, it will for sure remove that bottleneck on demand. I recently picked up an SC-88 for a decent price, but they are going up now too.
Anyway, thanks again! I just heard Wing Commander through the MT-32 for the first time. So much better!