In their waistcoats, prospector's boots and stiff, unfaded Wranglers, Mumford and Sons look like a gang of porch singers straight out of 19th-century-era Appalachia. But these twentysomething Brits were terrified of sticking out when they played Tennessee's Bonnaroo festival this year. "If I play my banjo badly in Britain, I can get away with it," says "Country" Winston Marshall, who started teaching himself to play at age 11. "In America, everybody knows if you're crap."
They shouldn't have worried about their stateside reception: Their debut album, Sigh No More, full of foot-stomping tunes and Steinbeckian lyrics that wrestle with faith, broke Billboard's Top 20, and they played their Hot 100-cracking single, "Little Lion Man," on Letterman.
The foursome got together five years ago at a London-pub country night, bonding over a bluegrass version of Gnarls Barkley's "Crazy." Mumford and Sons (the name was meant to evoke an old family business) initially formed to record frontman Marcus Mumford's songs but quickly morphed into something more democratic. "We're like brothers," says keyboardist Ben Lovett, "and we try to run the band that way."
This story is from the October 14th, 2010 issue of Rolling Stone.