Mumford and Sons have unveiled a new track, "Learn Me Right." The folk-rock group collaborated with vocalist Birdy - who sings lead on the song - which is included on the soundtrack to new animated film Brave.

"It's quite fun doing a song for a movie rather than for an album. We liked the idea of having an orchestra in the background and having a girl like Birdy sing - it's been quite liberating," frontman Marcus Mumford said.

As well as the one-off song on the soundtrack, Mumford and Sons have recently recorded their much anticipated second album, the follow up to 2009's Sigh No More, but Keyboard player Ben Lovett has warned they are prepared to scrap the whole thing if it doesn't meet their high standards.

"We've done recording it but if we listen back while we're mixing and discover it's s**t then we'll just start again. We're not going to put it out until it's good enough," he said.