Best known as the composer of the lilting "Gentle on My Mind," the country-pop gem that jump-started Glen Campbell's solo career, John Hartford lets his freak flag fly on Mark Twang. Sawing his fiddle, picking his banjo and guitar, tapping his feet, and emoting about steamboats, the Mississippi River, his bluegrass heroes, and reefer, Hartford sounds like he's engaged in a scintillating interior dialogue that we get to eavesdrop on. Some of the tracks are downright bizarre, like Hartford's vocal pyrotechnics on "Little Cabin Home on the Hill Waugh Waugh," his recreations of a vinyl record skipping on "Don't Leave Your Records in the Sun," and his stoned, absurdist spin on the Lord's Prayer, "The Lowest Pair." But Hartford is a virtuoso instrumentalist, as "Austin Minor Sympathy" demonstrates. Mark Twang may dismay purists with its engagingly wacky, unapologetic hippie outlook, but it's an album that brought the music to a generation weaned on rock 'n' roll but longing to get back to the country.