O.C.M.S., the debut album from bluegrass group Old Crow Medicine Show, is a corker. The soundtrack to O Brother, Where Art Thou? had a mass appeal that brought bluegrass to an entire audience who didn't know they could like bluegrass; with any luck (and a boost from an appearance on Late Night with Conan O'Brien), O.C.M.S. is likely to do the same. The band name evokes something fiery, hard to swallow (have you ever tried Old Crow?) and some kind of backwoods soapbox sleight-of-hand. And true to its name, OCMS weaves a coarse magic around the listener's head with its blend of rowdy honky-tonk and soulful bucolic lament. O.C.M.S. is at its best when it turns from raucous to plaintive, as with "Hard to Tell," "Take 'Em Away," the mournful "We're All in this Together" and "Wagon Wheel," perhaps the catchiest tune in an album of catchy tunes. "Wagon Wheel" especially clips along at a toe-tapping pace on a wave of fiddle and vocal twang, a wistful tune engendering equal parts wanderlust and the need to sing along. Whether their salt-of-the-earth sound is a gimmick or sincere, Old Crow Medicine Show is a breath of fresh air in a sea of new music where it's often impossible to differentiate one metal rap or sensitive-boy maudlin introspection from another. Popular music needs more harmonicas, fiddles and banjos.