When you've sold millions of copies of your debut album worldwide with a sound that had never shown much commercial potential, what do you do for an encore? That's been the problem faced by Mumford and Sons. The British folk/bluegrass purveyors have been working since August on the follow-up to their 2009 smash, 'Sigh No More,' but are not sure if it will be released in 2012.

Speaking to NME, singer Marcus Mumford said the delay was due to them not wanting to "put that added pressure on ourselves. Everyone's just letting us get on with it. The only people that have heard it are [producer Markus] Dravs, our manager and us. No-one else has been involved in the process."

Mumford did say that the album would be an "evolution, not a revolution" from 'Sigh No More.' ' However, contrary to what bassist Ted Dwane told Rolling Stone in December, it will not create the genre of "doom-folk," which is formed when "Black Sabbath meets Nick Drake."

"That was a joke to an American journalist who didn't understand the concept of sarcasm," Mumford said. "I called Ted and was like, 'Ted, what have you done? We spent our whole first album trying to avoid being pigeonholed!'

But the band haven't spent the entire time locked away in the studio. On March 14, Mumford and Sons performed at the White House at a state dinner for British Prime Minister David Cameron. They then flew to Austin for SXSW, where they performed some of the new songs and attended the premiere of 'Big Easy Express' a documentary of their tour with the Old Crow Medicine Show and Edward Sharpe and the Magnetic Zeros.