The MT-32 version of the #TransportTycoon soundtrack sounds so warm, I very much prefer it to how other synths (Fluidsynth, Timidity) play the General MIDI version.
Now if I could find a way to dump the MIDI data from the DOS version of the game *and* the SysEx for the custom MT-32 patches I could make #OpenTTD route the MT-32 version with a custom player command to Munt 
…and people has been woerking on adding an #AdLib emulator in OpenTTD to support playing music from the “adlib.cat” file. This seems to have the same (similar?) format as the “gm.cat” one, modulo the MIDI data is intended for OPL2/OPL3 playback.
Branch here: https://github.com/nielsmh/OpenTTD/commits/adlib-music
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Okay, digging a bit in tt-forums.net it seems that people have already figured out that the “lapc1.pat” file contains the the sound patches (hopefully as some kind of SysEx data), and that the “roland.cat” file has the music and that it should be somewhat similar to the “gm.cat” one with the General MIDI version of the songs.