Keira Knightley has said that singing in her new movie Begin Again left her 'completely terrified'.

The actress, who stars alongside Maroon 5's Adam Levine in the film, told the Associated Press about stepping outside of her comfort zone, "I was completely terrified. I didn't anticipate being as frightened as I was.

"I said yes to doing it and I was [like], 'Oh, it's gonna be fine, it's gonna be fine', and then suddenly I found myself in a studio with real people who did it for a living and I was like, 'I don't know what I'm doing. I'm pretending'."

Begin Again premiered at the Tribeca Film Festival on Saturday, April 26, and sees Knightley and Levine playing college sweethearts pursuing a career in music in New York City.

The film was written and directed by Irishman John Carney. Hailee Steinfeld and Mark Ruffalo also star in the film, which is set for release on July 11.