Britney Spears Collaborates With Black Eyed Peas' Will.I.Am On New Track

Britney Spears partnered up with Black Eyed Pea's will.i.am (only her second collabo ever!) for a track entitled "The Big Fat Bass", which Will teased a snippet of this morning.

This is the third "tease" that Britney has released in recent weeks, albeit the only one not from her forthcoming album, Femme Fatale.

Britney, singing backup for the Pea's frontman coos "I can be the treble, baby, you can be the bass," in the short tease for the new single.

On his blog, will.i.am writes, "thank you britney for collaborating it was a pleasure working with you. thank you for trusting my instincts. you're a doll. i look forward on working with you again... its an honor because you rarely do collaboration... im your second..."

Actually her collaborating on someone else's track isn't the only out-of-character thing about this -- take a listen below and see if she reminds you of some other pop star whose prone to making guest appearances...