Hi,
this works for me
[midi]
mpu401=none
mididevice=synth
midiconfig=”/storage/9C33-6BBD/Android/data/bruenor.magicbox/files/win/SoundFonts/GeneralUserGSFluidSynthV1-44.sf2″
I tested it on game Gooka. Without it i get strange sounds. With this is midi working. I think it should work with mt32 roms as well, but who knows, i didnt try