I know you haven't gotten to sound yet, but I'd like to ask some questions and make some suggestions regarding sound and music, if you don't mind?
I expect you're going to have some trouble with this. Other than the PC beeper, modern computers and operating systems are not able to provide reproduction of any of the sound modes supported in the original game.
* The adlib/soundblaster mode works by writing registers to the appropriate I/O addresses of the original hardware. None of this in any way will work on a modern computer. You might be able to bundle in a free/open OPL emulation engine, such as those used by DosBOX.
* I don't know anything about Tandy/PCjr mode, but I expect it'll be in the exact same boat.
* The MIDI data present in the game is targeted for the pre-General-MIDI Roland MT-32 and it's descendants such as the LAPC-I and CM-32L. This hardware is extremely scarce, and while the excellent MUNT project can provide an authentic emulation, it requires firmware dumps that Roland's lawyers have made a pain in the ass of themselves about. I would suggest it makes little sense to committing programming time to implementing support for hardware that's almost non-existent in today's world.
Of these sound modes, the Roland will offer by *far* the most robust music reproduction - see this for an example:
Many other efforts to re-implement DOS games of this era have gone the route of enhancing or replacing the music engine to play looped OGG files on demand, and I have been happy to provide high-quality Roland music packs for these games. This same approach also allows for a third-party to create highly-authentic Adlib/Soundblaster packs, someone could even roll together a Tandy music pack if they were so inclined. Or a musically-talented individual could produce and distribute completely new and custom music!
Civilization presents an additional challenge in that what limited sound effects the game has are also reproduced via the same synth method - In the case of Roland, the game plays back custom instruments as needed to produce the effects. The only sound effects the game does, so far as I remember, is a "skirmish" or "cannon" sound during combat.
If we can nail down the specifics of how the files need to be formatted and laid out, I'd be delighted to start putting together a Civilization Roland music pack for you.