Just beat me to it
Cage had studied Zen Buddhism and claimed that any auditory experience can constitute music, and so he came up with 4'33". Her mother probably wouldn't have been too impressed though.
When I was at university, there was a "concert" performance of his "Branches" at the aula (concert hall). I didn't go, but I heard afterwards that there had even been an encore, although that might have been a joke.