Harmonix has confirmed that Rock Band 3 will support vocal harmonies.
According to Joystiq the news emerged at PAX East. "We've said Rock Band 3 would have harmonies already, right?" project lead Chris Foster asked his fellow panel members. "No!," they replied, in harmony.
Vocal harmonies were developed for and debuted in The Beatles: Rock Band last autumn. They were more difficult to sing than regular melody lines, but the game came with a trainer that laid-out the basics brilliantly.
What we know about Rock Band 3 so far is that there will be one. Harmonix has claimed the game will "revolutionise the genre", but said no more on Natal/Move support or whether the rumours of a keyboard peripheral are true.