Manual: {F15992}
May not be the manual for my revision per se, as setting reverb does not appear to be as mapped, or maybe I'm reading the manual wrong.
Other stuff:
* Some patch files and old DOS utilities: http://www.midimusicadventures.com/queststudios/mt32-resource/
* Semi-old Java app: http://www.jsynthlib.org/
I have a real one, but emulation is probably an easier time for most! And https://github.com/dwhinham/mt32-pi uses http://munt.sourceforge.net/ to even provide a cheap dedicated hardware reimplantation.