Justin Timberlake revelead to Capital FM in the UK that he's done a song with Marcus Mumford, the frontman for Mumford and Sons, for the new Coen Brothers film that JT is in. 

The track also features producer T-Bone Burnett and bluegrass band the Punch Brothers.

Justin said: 

"Ok I can tell you this. There's a Coen brothers film coming out soon that I was lucky enough to work with Oscar Isaac and Carey Mulligan and coincidentally I did work with Marcus Mumford on the soundtrack, so I became very good friends with them. 

"Marcus and myself we all kind of worked on the music together and I don't know any other world where we would have the opportunity to collaborate like that but it was so much fun. So not only will that be a great movie, but the music to it will be fantastic."

Marcus has also said in a recent Rolling Stone interview that Mumford wants to rap "Like, hip-hop. We really want to rap. We've just got so much to say — saying it through a melody doesn't really work for me. We've been talking with Jay-Z about it, you know. It's gonna be a fresh experience for our band."