Files for mt-32 were copyrighted. I heard that copyright already expired, however I am aware post files, because I have no more details.
But try searching for “vogons mt-32 roms” in google search engine.
My files have size CM32L_CONTROL_ROM (65536B) and CM32L_PCM.ROM(1048576B)
I own roland
For synth(soundfont) you need sound fonts – files with extension .sf2 (for example FluidSynth.sf2, SGM-V2.01.sf2, mt-32.sf2, GeneralUser_GS_SoftSynth_v144.sf2, etc)