Gaga teams with Paul McCartney

Sir Paul McCartney and Lady Gaga are collaborating on a "secret project".

After teaming up with Kanye West and Rihanna on new music for their respective albums, the Beatles legend has now recruited the quirky diva to work on some music of his own.

Taking to Instagram, Gaga shared several photos with fans as she hinted at an exciting new project in the works.

"Had a beautiful session with Sir Paul McCartney and friends. Working on one of his many secret projects! Killer musicians, vibe, and lots of laughs," she captioned a group shot featuring herself and Paul surrounded by a dozen musicians.

A second image captured the 28-year-old pop star looking mighty happy with herself as she flashed the peace sign, her arm wrapped around the 72-year-old as he sat at his drum kit. The photo was well-received by fans, who were seemingly thrilled at the prospect of a collaboration.

"Always a good time with my buddy," Gaga wrote to accompany the snap, adding the funny anecdote, "I'll never forget when he called me last year to work and I hung up the phone cuz I thought it was a prank (sic)!"

While their collaboration was seemingly a long time in the making, both parties have managed to keep it quiet, with little known about just what this "secret project" will consist of.

Of course, after joining forces with Rihanna and Kanye West on the single FourFiveSeconds from the 26-year-old R'n'B star's upcoming album, #R8, as well as teaming up with Kanye, 37, for the duet Only One, fans can surely expect plenty of A-list surprises.

Rihanna has just released the video to accompany FourFiveSeconds – a low-budget production featuring all three stars dressed in denim against a plain white background, shot in black and white.

Paul plays the guitar and sings harmonies as Rihanna and Kanye sing the vocals.

British newspaper The Sun reported last week that the trio will perform at the Grammy Awards in LA this Sunday, with the song already a certified smash hit around the world just one week after its release.