DC in December; what a treat especially for music. Although it looks like you have lots of suggestions from other Ziners for Sunday concerts, here's one more. The National Gallery hosts free Sunday night concerts at 7:00pm. A nice evening out is dinner at the museum and then the concert afterwards. By arriving early for dinner, you are there to get a seat when the doors open. The music is supurb and the venue, gorgeous. Here's a link for the schedule:

http://www.nga.gov/ginfo/clndrdec.htm

I must also put in my two cents for dining in the Capitol. For a fun local kind of lunch, stop by Scholl's Colonial Cafeteria (1990 K Street). It's a bit of an institution and serves good, hot, home-style cookin. For something a little swankier; I would suggest the 1789 Restaurant in Georgetown (1226 36th St. NW) . It looks like an elegant country inn and serves wonderful classic dishes.

Have a great trip! Dawn Philadelphia, PA