You won't be far from Westminster, MD, which has some great music. Check out Common Ground On The Hill. Unfortunately, it looks as though their concert series is monthly and won't have anything on while you're there. Cephas and Wiggins on January 6 looks like a great show.
If you are making the trek to Nazareth, PA to visit Martin Guitars, you might plan a visit to Godfrey Daniels in nearby Bethlehem, PA.
And in Philadelphia, you can check out The World Cafe Live.
Enjoy your visit.