"Had a beautiful session with Sir Paul McCartney and friends," Gaga wrote on Instagram, alongside a photo of herself, Macca and a room full of instrumentalists -- including none other than Pearl Jam guitarist Mike McCready, on Gaga's right. "Working on one of his many secret projects! Killer musicians, vibe, and lots of laughs."
But that wasn't the only photographic tease: Gaga also posted a solo pic of just her and McCartney, recalling the first time she heard from the rock-and-roll icon -- and promptly hung up on him.
"Always a good time with my buddy," she wrote. "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!"
So how will this collaboration turn out? Will it be only his guitar work, in the vein of his recent work with Kanye and Rihanna? Or maybe Gaga has her sights set on a new partner, after her No. 1 duets album with Tony Bennett? We'll have to wait and see.
Requests for further details from McCartney's rep went unreturned at press time.