John Gage
Silence. Not silence.
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Although commonly perceived as "four minutes thirty-three seconds of silence", the piece actually consists of the sounds of the environment that the listeners hear while it is performed.
In 1951, Cage visited the anechoic chamber at Harvard University. An anechoic chamber is a room designed in such a way that the walls, ceiling and floor absorb all sounds made in the room, rather than reflecting them as echoes. They are also externally sound-proofed. Cage entered the chamber expecting to hear silence, but he wrote later, "I heard two sounds, one high and one low. When I described them to the engineer in charge, he informed me that the high one was my nervous system in operation, the low one my blood in circulation."