They gave a sold out performance at the Hollywood Palladium last night but you've probably never heard of them. The band members play multiple instruments including banjo, accordion, string base, mandolin, keyboard, drums and guitar (which the lead singer sometimes plays at the same time)-- yet they aren't a bluegrass band. They're not even Americans; they're a group of four young Englishmen. It's hard to classify Mumford and Sons' music, but the closest description is probably "folk rock." Their most popular song, "Little Lion Man" is junked up with a curse word, but an edited version is played on the...