SimCity 2000 in DOSBox has 1 option for sound effects, and 5 options for music! DOSBox seems to emulate an IBM PC speaker, a Sound Blaster 16, and an MPU-410 MIDI device. Sound effects always go to the SB16. Music can go to the PC speaker, to the SB16's FM synthesizer, or to MIDI; the game has 3 different MIDI banks.
For sound effects, I use Sound Blaster 16 (GOG's default). Some other options do work, because the SB16 is compatible with some other sound cards, but they all seem to sound the same in DOSBox.
For music, your 5 options are:
1. Roland MT-32/LAPC-1 (GOG's default) plays MIDI with MUSICFILES=MT
2. Wave Blaster plays MIDI with MUSICFILES=WB
3. MPU-401 General MIDI plays MIDI with MUSICFILES=GM
4. Sound Blaster 16 uses FM synth, sounds more artificial
5. PC Speaker beeps, sounds awful
DOSBox always plays MIDI through your computer's MIDI synth. All 3 options (MT, WB, GM) use the same synth; the only difference is in the music from the game. Roland/MT might use more instruments, so it might sound better than WB or GM. If you change the MIDI synth or soundfont in your computer, it would be like a different band playing the same music.
If you pick SB16 or PC Speaker for music, then DOSBox emulates the synthesizer and plays the result on your computer's audio, so you don't need a real SB16 or PC Speaker. I have switched to the Sound Blaster 16 for music. The SB16 sounds less like real instruments, but pairs well with the graphics of SimCity 2000.