John Cage's most famous piece has no notes in it, and it isn't silent.
In 1952 a pianist walked on stage, closed the keyboard lid, and played nothing for four minutes and thirty-three seconds. The audience thought it was a joke. Cage's point was that true silence doesn't exist: the coughs, rain and rustling in the room were the music.
The pianist David Tudor gave the premiere of 4′33″ on 29 August 1952 at the Maverick Concert Hall in Woodstock, New York. He marked the start of each of the three movements by closing the keyboard lid and the end of each by opening it. The score tells performers of any instrument not to play. Many in the audience took it as a joke or an insult, and some did not realise a piece was being performed at all.
Cage had toyed with the idea for years. In a lecture around 1947 he described wanting to write a piece of uninterrupted silence called Silent Prayer and sell it to the Muzak company. Two experiences pushed him to do it. In 1951 he visited the anechoic chamber at Harvard, a room built to absorb all echo, and still heard two sounds, which an engineer told him were his nervous system and his circulating blood. And his friend Robert Rauschenberg had painted all-white canvases whose appearance changed with the light and shadows of the room.
Cage was not the first to write silence. Alphonse Allais published a funeral march of 24 empty bars in 1897, and Erwin Schulhoff wrote a movement made entirely of rests in 1919, though Cage said he had not known Allais's piece. But Cage meant his seriously, drawing on his study of Zen Buddhism: the piece asks listeners to attend to whatever sounds are around them.
It still provokes. In 2002 Cage's heirs pursued the musician Mike Batt over a track of one minute's silence credited to 'Batt/Cage'; he paid a reported six-figure settlement, then admitted in 2010 that the dispute had been a publicity stunt and he had only donated £1,000. That same year a campaign to make 4′33″ the UK Christmas number one got it to number 21. Cage called it his most important work.
Source: Wikipedia — 4′33″ · Text summarised from Wikipedia (CC BY-SA 4.0)