Even though everyone pretty much assumed that Rock Band 3 would be coming with harmonizing vocals like The Beatles: Rock Band and Green Day: Rock Band are, it was never confirmed. That is, until yesterday. During a PAX East panel Harmonix's Chris Foster inadvertently revealed that the upcoming sequel would indeed include harmonies.

The actual reveal came when the panel was asked if Green Day tracks imported into Rock Band 2 would still use harmonies. In response, the developers began listing the games that would work with harmonies, and Foster accidentally dropped this gem.

"We've said Rock Band 3 would have harmonies already, right?"

Jokingly, after realizing that feature had not actually been made public, Foster said , "It's been nice working at Harmonix." While it's not that surprising to hear, it is actually pretty cool. Harmonizing in The Beatles: Rock Band was really cool, and is a feature that should make singing in future games a lot more fun. It also opens up the game to even more players than before, and if my experiences are any indication, harmonies will definitely keep the party lively. As much fun as Rock Band is with just four people, adding two more vocalists to the mix really gives the illusion that you're performing in a live concert. Well, you know, as live a concert as you can have in your living room... with fake instruments... and no audience.

[Source]