Paul McCartney's newest project is sure to test the loyalty of even his most devout fans. The singer and former Beatle is eagerly anticipating the opening of his first ballet next month. McCartney wrote the music and had a role in designing sets, costumes and choreography for 'Ocean's Kingdom.'

In the video below, one sees the about to be re-married singer working with dancers, the director and even the costume designer (his daughter Stella got that job). During an interview alongside New York City Ballet’s Master in Chief Peter Martins, McCartney says it was Martins who suggested the idea to him.

"I had started a piece of music for another project that didn't work out," McCartney says. "So when Peter asked me, 'Would I consider?' I immediately thought of this other piece of music. And I thought, 'Yeah, this is what I should do with this other piece of music.'"

"I had no idea what the rules were or if in fact if there were any. So I just went back and wrote music with dance in mind, that excited me and that I thought would excite Peter."

Classical music is a long way from the pop sound the singer practically invented five decades ago, but McCartney had already been working in that genre. He was glad to be invited to play an active role in the direction of the ballet, which opens Sept. 22 at the New York City Ballet. The soundtrack is available at McCartney's website on Oct. 4.

Watch a preview of 'Ocean's Kingdom' and an Interview with McCartney