Just FYI: I know what a real Roland MT-32 sounds like. I recorded these videos a while back with a real Roland MT-32 and my MiSTer
Flashback --> http://y2u.be/8FfU6gpbF28
Ultima 6 --> http://y2u.be/DZs6KVA4zvU
The problem is that the ARM CPU is on the low end of the requirements for MUNT. I think it can be better with compiler and run-time optimizations.
-m : Manual buffering mode (buffer does not grow)
-a : Automatic buffering mode (default)
-x msec : Maximum buffer size in milliseconds
-i msec : Minimum (initial) buffer size in milliseconds
-l mode : Analog emulation mode (0 - Digital, 1 - Coarse, 2 - Accurate, 3 - Oversampled 2x, default: 2)
You could also try a MT-32 SoundFont with FluidSynth, but that will only work for things that don't reprogram the MT-32's default soundbank.
You can also use the UDP option to send the raw MIDI data to MUNT running on your desktop PC.