I see Sergm might be the one to look into this.

I have 2 programs.. runs on simcoupe (Zx spectrum) emulator
I can provide a disc copy of it free

first program is MT-32 writer.. it sends characters to the mt-32
LCD and scrolls it.. up to 19 chars.. but fails on emulator

2nd program is more fun,,, it allows to modify the samples
sounds parameters.. so you can change how they sound
like the funkyvox can make it sound like a choir boy
but it dont work.. it uses SYSex

2nd one uses MDOS so have to boot to it first
perhaps sergm could email me for a copy to play with
and see why it hangs., or interested in this function
i wrote it back in 1998 and forgotten all the tech and coding
thought but it uses mostly basic peeks and pokes

can contact me for copy at artbiz2000@hotmail.com