MTV, EA, and Harmonix today officially announced that Rock Band 2 will debut on the Xbox 360 first this September and will appear on other systems later in the year.

• Xbxo 360 version will come out first.
• RB1 instruments will work with Rock Band 2 and vice versa.
• New and improved official instruments will be available, but they are also working with third party companies to give gamers a huge variety of guitars/etc. to choose from.
• RB 1 downloadable content is fully compatible with Rock Band 2.
• Improved online modes. Better single-player modes. Pretty much better everything.

For more information, check out RockBand.com and HarmonixMusic.com.