The original DOS port of Ultima IV has no music or mouse support. There is an upgrade patch available that upgrades the graphics and adds music, but supposedly the patch only works when running the game under Windows.

EDIT: Just for grins I applied the upgrade patch to see if it works. Well it seems to definitely add the music, but not so sure about the updated graphics since I didn't have time to play the game past the intro. Anyway, I put the updated version up for download through RubyBox and also exported some settings to the database that seem to allow the game to run fine with the music and sound. If there are any problems let me know since I haven't thoroughly tested the game.

EDIT2: Yes the graphics are updated in this version too. Even though the update page says it won't run in DOS, it does seem to run fine in DOSBox! Very nice!