In February, Lady Gaga posted a photo of herself in the studio with Paul McCartney, and revealed that they were “working on one of his many secret projects!”  The cat is out of the bag with that secret: a new song from an upcoming movie.

The new issue of the British magazine Q reveals that Gaga and Paul collaborated on a song in Los Angeles for an upcoming animated film called High in the Clouds. It’s based on a 2005 children’s adventure novel co-written by Paul, about a squirrel whose woodland home is destroyed by an evil developer.  He bands together with a few other woodland creatures to save enslaved animals everywhere.

This is the second time that Gaga has teamed up with a British rock legend for an animated film: in 2011, she and Elton John worked together on a song called “Hello Hello” for the movie Gnomeo & Juliet.

Paul tells Q magazine that when his assistant called Gaga up to get her on board for the collaboration, she hung up on the guy because she thought it was a joke.  So Paul himself called, asked for Gaga by her birth name, Stefanie, and, he says, “tried my best to sound like me.”

The ex-Beatle says he wasn’t angry at Gaga because, as he explains, “I’m conscious of people thinking it’s a mate at work, and saying ‘Oh, f**k off, Fred!  Stop doing your McCartney impression!”