Rock Band 3 players will be able to download the rest of John Lennon's Imagine album soon.
http://www.nintendoworldreport.com/news/24351
Harmonix announced today that the entirety of John Lennon's Imagine album will be one of the first albums available as downloadable content for Rock Band 3.
The headline track of the album, "Imagine," is already included on the disc. There are nine other tracks on the album, including "Jealous Guy" and "Gimme Some Truth." The full track listing is below.