Great news on this!
I've unfortunately not got it to work
The only game I'm running at the moment with MT32 support is Leisure Suit Larry 6 (CD talkie edition).
I uninstalled the existing MT32 driver (canadacow's version). Installed 'Munt'. Configured the preferred MIDI device to be the MT32 Synth. Re-ran the Sierra installer, selected MT32 as the music device. Left VDMSound as General MIDI emulation.
Run up the game, and I get a 'start of a sound' then silence. Nothing from then on is played. If I reconfigure LSL to use a Soundblaster then I get the Sierra fanfare as I'd expect.
Anyone got any pointers for me or can I provide any diagnostic infomation?