Interesting… I should investigate it myself now that I got the GOG version alongside my “alternative source” copy.
Edit: I just tried, and with GUS=TRUE in the DOSBox configuration file, and ULTRADIR pointing to the appropriate patch directory, I get music and sound with the GUS option, both in my own DOSBox collection, and in the GOG version I just installed.
It sounds the same as the Soundblaster option, though, which is what I would expect, really, given that the music is tracker (PSM) and not MIDI.
What am I missing?