Mike Seeger. He emceed a workshop at that fest. (??early seventies) on barbershop quartet harmony. A female quartet was on, and I was so impressed with Mike's questions; he had them describe how they laid out the melody first, then usually the descant, bass and alto. How they built the harmony. It was great.
I discovered Louis Killen at that festival (probably not he same year). and got in some clogging practice. (I had taken Sharee Shepherd's clogging class, with a to-remain-nameless live musician friend, and it was hard to find places to practice afterwards.)
Boy, those were good times.