Basically if you want keyboard and vocal support for your old Rock Band tracks, then you’re going to need to buy them again in their Rock Band 3 format.
”To reiterate, if you stick with your RB2 legacy track and want to upgrade to pro guitar/bass – you will not have access to Keys, Pro Keys or harmony vocals. If you want that latter content, you need to purchase the “RB3 Version” of the file,” posted Harmonix.
It would appear this whole DLC market is getting a bit messy with its selection, and it’s pricing. The only upgrade for oldie Rock Band tracks is to add Pro Guitar and Bass which costs 80 Microsoft Points/£0.59 - otherwise you have to buy the RB3 version.
Today they’ve added 12 Bon Jovi tracks and 1 for Deftones, New Order and Talking Heads. Each is £0.99/€1.49/160MSP or £9.99/€14.99/1600MSP for the Bon Jovi Greatest Hits: Rock Band Edition. This latest Rock Band hasn’t been doing so well in sales.