To no one's surprise, Harmonix, MTV and EA are preparing an encore for Rock Band later this year. Rock Band 2 is now official -- and it's coming to Xbox 360 this September, with "other platforms" releasing later in the year.

Before you start deleting the dozens of tracks you've downloaded for the first Rock Band, know that RB2 features ground-breaking cross-title compatibility. There is no distinction between Rock Band 1 and Rock Band 2 DLC. Any DLC you've previously downloaded will instantly work with Rock Band 2 and all DLC will continue to work with the original game from here and into eternity. While Harmonix has yet to reveal the number of tracks included on the RB2 disc, with the inclusion of all the previously released DLC, the set list at launch may top 300 songs.

"As successful as the original Rock Band continues to be, we've now had the benefit of the last eight months to listen to our fans' requests and to build upon that foundation," said Alex Rigopulos, co-founder and CEO of Harmonix. "Rock Band 2 is a second-generation band game that will elevate the music game experience to the next level."

As with Activision's recently announced Guitar Hero World Tour, Rock Band 2 features all master recordings on disc. You can also expect major improvements to online functionality and a more "party friendly" set-up so it's easy to get guests rocking out faster.

While all RB1 peripherals will work with the sequel, upgraded versions will be available in a bundle pack. Harmonix isn't revealing what these upgrades are just yet.

Rock Band downloads will continue to arrive weekly for both Xbox 360 and PS3. Each track you purchase is essentially extending your library of Rock Band 2 tracks. And even though PS3 owners will have to wait longer to get Rock Band 2 on disc, they will still have access to new downloadable content with RB1. With Rock Band DLC having now surpassed 15 million paid downloads, there appears no end in sight for the most successful digitally distributed product on 360 and PS3.

So why release first on Xbox 360? "Microsoft has been a great partner throughout the launch of Rock Band in the last year and their continued support is instrumental in supporting the more advanced features and cross title compatibility we will have in Rock Band 2," a Harmonix representative told IGN. "Of course, our goal is to make Rock Band 2 accessible to all and we look forward to bringing Rock Band 2 to all relevant platforms later this year."

For more details on Rock Band 2, check out IGN's exclusive interview, which is packed with info.