Mandolin? No. Guitar? Sparingly on two tracks. Cello? You bet your arse. Boston-based quartet Crooked Still are bluegrass experimentalists, not mere new grass revivalists, taking traditional American roots music and—through inventively fresh arrangements, adding that unlikely cello to banjo, sumptuous harmony vocals, and double-bass, with occassional fiddle—deliver a deep-down-in-the-barrel acoustic sound that rocks the foundations of classic songs, such as the 1920s murder ballad “Little Sadie” and the gospel-blues recording “Ain’t No Grave”, without losing their authenticity. When these classically trained musicians cut loose on their sophomore release and yield up gems like a party-stompin’ version of Bob Dylan’s “Oxford Town”, or the toe-tappin’, smoky-jazz take on Bill Monroe’s “Can’t You Hear Me Callin’”, you begin to wonder why no one ever thought about dragging a cello up into the Appalachians back in the day. But then, maybe the answer is in the question.