Mumford & Sons have an unusual sense of timing. Gallery: Mumford and Sons Gallery: Mumford and SonsThe mustachioed, gum-chewing Mumford, 39, was a friendly and often funny frontman. "Stomp clap repeat" was a hallmark (oops unintended pun) of Mumford & Sons' concert. Mumford & Sons are considered the progenitors of the stomp-clap-hey movement of mixing bluegrassy folk-rock with a foot-stomping rock beat and sing-along choruses. Mumford & Sons' distinctive production was scaled perfectly for the Shakopee amphitheater with its tall stage opening.