John Cage performing "Water Walk" in January, 1960 on the popular TV show I've Got A Secret.

via WFMU:
http://blog.wfmu.org/freeform/2007/04/john_cage_on_a_.html

"At the time, Cage was teaching Experimental Composition at New York City's New School. Eight years beyond 4:33, he was (as our smoking MC informs us) the most controversial figure in the musical world at that time. His first performance on national television was originally scored to include five radios, but a union dispute on the CBS set prevented any of the radios from being plugged in to the wall. Cage gleefully smacks and tosses the radios instead of turning them on and off.

While treating Cage as something of a freak, the show also treats him fairly reverentially, cancelling the regular game show format to allow Cage the chance to perform his entire piece. " (less info)