John Cage's '4:33'

Extracted from The Rambler blog post: "John Cage Uncaged: Barbican Centre, London, 16th-18th January 2004":
Cage’s method does have an equalising effect - this was at the core of much of his philosophy - but it is a mistake that the individual elements are brought down to the same level. Cage’s genius - and why, in fact, the ego of the composer (wherever that might be) is still crucial to his music - is to elevate these elements above everything else. All sounds may be created equal, but the ones Cage asks you to play are more equal than others. Thus 4′33″ isn’t constantly playing as ambient background Muzak to our lives: the opposite is true, and it is only playing when we (or another performer) decides when it is to begin and end. It is actually the least ambient work in history, since it only begins when someone starts to listen to it.

John Cage @ Wikipedia