It's hard to overstate the impact that Dr. Ralph Stanley has had on bluegrass and old-time gospel music. Now 82, he sits atop a 60-year legacy of making music, both as the preeminent purveyor of clawhammer-style banjo picking and as a singer with one of the most widely imitated (but never duplicated) voices in country music. For this short Tiny Desk Concert, Stanley performs three classic songs, all a cappella: "Gloryland," "Turn Back, Turn Back" and "Amazing Grace."