Johnny Cash and John Hartford playing a medley of Bill Monroe songs (Monroe was the originator of the style of American country music known as "bluegrass"). Hartford was a bluegrass musician who wrote the song "Gentle on My Mind", which was a huge hit for Glen Campbell. Hartford also contributed to several songs on the "O Brother, Where Art Thou" soundtrack. (Songs in the medley: "Muleskinner Blues", "Columbus Stockade", "Blue Moon of Kentucky" and "Uncle Penn".
This aired on August 23rd, 1969.