I'm getting to like the Root Cellar more and more, but there is no live music. Still, it is small and kind of cozy and would be a good romantic start to the evening.
As for the music, it depends on the type of music and the night. I don't get out for music that much anymore, but I always liked the Cheatham Street Warehouse. Please don't anyone tell me it is closed down or something.
Then again, dinner at Huisache and beers at Gruene Hall could be cool too. You gotta leave San Marcos for that, though.