Mumford & Sons + Dawes + Aaron Embry

They've come a long way, baby: Having emerged from London's thriving folk scene, Mumford & Sons' gravelly bluegrass debut, Sigh No More, became one of last year's biggest hits. The band's sweaty, exhilarating live shows are already the stuff of legend (or at least breathless reviews), so this outdoor party promises to be quite something.