Listen to Keira Knightley sing in an exclusive clip from People magazine for her new comedy-drama, "Begin Again" HERE!

Knightley sings a newlywritten breakup song into the voicemail of her now former beau, Dave, played by Adam Levine. British actor and Tony Award winner James Corden plays the keyboard and plastic kazoo in the clip.

The story of "Begin Again," which is written and directed by John Carney, is as follows: "Gretta (Knightley) moves to New York City with her boyfriend and songwriting partner Dave (Levine), but soon becomes a mere accessory and then an emotional inconvenience when he becomes a hot, up-and-coming star. She crashes with an old friend (Corden) and starts making her own music with the encouragement of a burned-out music executive (Mark Ruffalo)."

Begin Again, which opens June 27 in limited release, is. Carney also made the hit movie Once (2006), which is now a Broadway musical.

Knightley revealed on "The Graham Norton Show" taht fans have approached her believing that she is Britney Spears.

The 'Anna Karenina' star said, "I get quite excited because I quite like the idea that I could do all that [mimes shimmying], which I can't do. So I've been Britney Spears like three times."

The actress said she is also frequently mistaken for Natalie Portman, even getting chased through airports by people who believe she's the "Black Swan" star.

Knightley admitted, "I feel quite sorry for her because she must get chased a lot because it's happened like five times where someone's been like [yelling] 'Natalie, Natalie, Natalie...' And I'll always sign and have a picture as Natalie Portman."

The Begin Again star also recounted how husband James Righton of the Klaxons tried to teach her how to play guitar for hew new musical film. Knightley said the lesson "nearly ended in divorce and murder."

Knightley said, "I've never been more angry. If you are married to someone, don't get the other one to teach you to play a musical instrument."