USA Today has a video posted of an exclusive look at Rock Band 3 and the details behind the illusive keyboard controller and how it will work in the series. The site has also revealed the first part of songs to be included with the game on release.
According to Harmonix, the keyboard controller will function both as a basic controller to play songs, or as an actual 25 key keyboard that players can use to actually learn the songs they play in the game. This is all part of what is going to be called "Pro Mode". Mad Catz will also be making both a Squier Stratocaster and mini Mustang bass that will also work dual function as both a game controller, and as a real instrument.
Rock Band 3 will also have full compatibility with all songs from earlier Rock Band games, though no details were given as to whether or not a code has to be purchased to move music like the previous title had. We can expect more details to come next week at E3. Hopefully this will whet your appetite until then.