I'd first like to say that this idea might not work for a number of reasons, but I just wanted to throw it out there for debate. I also would like to add that I am not an expert, and what I'm saying might not sound right.
There are a lot of songs that exist in the public domain, ones that artists are free to record. Some of these are traditional/folk songs, some were created specifically to not have ownership, some have rights that have expired, and there are probably others here too.
I'd think that these songs are probably also able to be created for Rock Band and uploaded to the Rock Band Network, once it gets going.
I know that I think that it'd be pretty cool to do some old ragtime songs, am imagining how cool a Spanish guitar chart would look, and loving the idea of a sing-along with She'll Be Coming 'Round The Mountain.
Anybody else think this would be cool/possible?