Gudadantza: I ignore if the GOG CD version has support for GM, but you could try to install the external General MIDI patch. I do not know if it was official or unnoficial but it can be worthy
https://wiki.ultimacodex.com/wiki/General_MIDI_Patches EDIT: I am pretty sure they are later unnoficial patches, so probably Ulima Underworld didn't support GM by default.
Greetings
teceem: Still, where would those GM/Adlib sounds come from? Doesn't DOSbox use the Windows default Midi device? (see my post for changing it)
Anyway, For Roland MT32 supporting games in Dosbox, I'd use Mint (+ROM) to get the best possible sound output.
Inosiphot: EDIT: I found a few options when pressing 2 to go to the settings, however there is no precense of a General MIDI sound option only PC Speaker, AdLib, SB, Pro and Roland.
teceem: AFAIK, most GOG Dosbox games are set up to use SB(Pro)... those sounds aren't built-in in Dosbox, they use the Windows default midi device.
My advice: look up tutorials on how to set up Mint.
Those sounds would come from his apparently well configured VirtualMIDISynth, because he says it works well in other games.