If you happen to have seen the Rock Band: Green Day demo that can be downloaded from Xbox Live, it teases a little of what can be expected in the upcoming Rock Band 3. There is nothing like a little cross-title marketing to get people excited these days.

Rock Band 3, as expected, will add keyboards to the mix. From the whispers we hear, the keyboard will be able to be purchased separately, so those that already have a previous Rock Band can add the keyboards to the mix.

In addition, it appears that Rock Band 3 will carry over the vocal harmonies technology that the company first offered in the Beatles: Rock Band title.

It is expected that we will get our first official look at Rock Band 3 during E3. Our sources tell us that Harmonix has a couple of other surprises in store for the third offering, as well. It will be just a couple of weeks to find out what they are.