Thanks for the help. The music-related bags are out of budget for me (I only spent $75 total on the bike, including the singlespeed conversion, light, and new seat). I have heard that some suitcases can fit the bike partly disassembled as well.
EAPellow, that sounds perfect. If there was a sturdy duffel with shoulder straps and room for bike+stuff, it would work out great. Let me know how it goes when you search for your own bike, I'm interested to see if it'll work for mine.