From the YouTuber who uploaded this gem:
"John Cale was the guest on this September 16, 1963 episode of I've Got a Secret. His secret centered around his participation in an 18 hour piano playing marathon that was the first full length performance of Erik Satie's "Vexations". (Not mentioned, John Cage was also one of the pianists.) Also on stage was Off- Broadway actor, Karl Schenzer, who's secret was that he was the only person to stay for the entire concert performance."