Looks like the "loose talk" surrounding vocal harmonising in The Beatles: Rock Band is spot on, according to retailer listings forwarded to Kotaku. According to retail game descriptions, the game supports three part harmonies.
That means support for three microphones at once, a new addition to the established Rock Band vocal gameplay style. Good thing the "limited edition" premium bundle comes standard with a mic stand. Now all you'll need are two more, plus a beefy USB hub to support all those inputs.
The official description, as forwarded to us, defines The Beatles: Rock Band as...
The Beatles: Rock Band is the music game experience that allows players to follow the legendary career of The Beatles from Liverpool, to Shea Stadium to Abbey Road. Featuring the ability to play drums, lead guitar, bass guitar or sing three part harmony with up to three microphones, The Beatles: Rock Band will focus on authentically recreating the feeling of performing The Beatles music on stage and in the studio.
We've contacted representatives from MTV Games to confirm the news, but have not yet heard back on the matter.