Oh. I see.
Not to sound ungrateful but I kinda thought the whole “20 free downloadable tracks” for Rock Band 2 owners might have included at least a few somewhat well-known tracks. Well it turns out that those 20 tracks are actually preselected from what MTV and Harmonix are calling the “Emerging Artist Lineup.”
On the bright side, they could very well be the greatest songs in the history of music. You never know. You… never… know. The tracks will be available November 4th. You can read the complete press release here, which includes the song list.