Sorry to dig up this thread, but it appears MUNT is now pretty much spot on. It now sounds almost exactly like a real MT-32 in the Daily Build of ScummVM! WOW!!!
Edit: The links in the first thread do not show the new version of MUNT in ScummVM. I've done a comparison myself, however, with the original MT-32 recording (at the top of this thread) and it's almost perfect. Amazing!