John Cage was a modernist composer famed for pushing the boundaries of what could be considered music.
"4:33" was famous for being debatably not-music. But... it is a good exercise for opening your ears to what's possible in improvisation.
In 4:33, the piece starts when the conductor lifts his baton or the pianist raises his hands to the piano - or any other signal that it's "starting." Then, for the following 4 minutes and 33 seconds, the musician does not PLAY any notes... the audience simply listens. Listens to the ambient noises.
This has the effect of shifting our perception: is that hum of the air conditioner music? Is the rhythm of that cough or sneeze in the audience musical? How about the siren of a passing fire truck?
I think the point is: anything can be music.
But I certainly wouldn't want to see this piece come up at a karaoke night!!! What do you think?