You Are Now Listening To John Cage's 4′33

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4′33″ (Four minutes, thirty-three seconds) is a three-movement composition by American avant-garde composer John Cage (1912–1992). It was composed in 1952 for any instrument (or combination of instruments), and the score instructs the performer not to play the instrument during the entire duration of the piece. 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. Over the years, 4′33″ became Cage's most famous and most controversial composition.

Conceived in 1948, while Cage was working on Sonatas and Interludes, 4′33″ was for Cage the epitome of aleatoric music and of his idea that any sounds constitute, or may constitute, music. It was also a reflection of the influence of Zen Buddhism, which Cage studied since the late 1940s. In a 1982 interview, and on numerous other occasions, Cage stated that 4′33″ was, in his opinion, his most important work.

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."

There has been some skepticism about the accuracy of the engineer's explanation, especially as to being able to hear one's own nervous system. A mild case of tinnitus might cause one to hear a small, high-pitched sound. It has been asserted by acoustic scientists that, after a long time in such a quiet environment, air molecules can be heard bumping into one's eardrums in an elusive hiss (0 dB, or 20 micropascals). Whatever the truth of these explanations, Cage had gone to a place where he expected total silence, and yet heard sound. "Until I die there will be sounds. And they will continue following my death. One need not fear about the future of music." The realisation as he saw it of the impossibility of silence led to the composition of 4'33″.

Cage wrote in "A Composer's Confessions" (1948) that he had the desire to "compose a piece of uninterrupted silence and sell it to the Muzak Co. It will be 4 [and a half] minutes long — these being the standard lengths of 'canned' music, and its title will be 'Silent Prayer'. It will open with a single idea which I will attempt to make as seductive as the color and shape or fragrance of a flower. The ending will approach imperceptibly."

Another cited influence for this piece came from the field of the visual arts. Cage's friend and sometimes colleague Robert Rauschenberg had produced, in 1951, a series of white paintings, seemingly "blank" canvases (though painted with white house paint) that in fact change according to varying light conditions in the rooms in which they were hung, the shadows of people in the room and so on. This inspired Cage to use a similar idea, as he later stated, "Actually what pushed me into it was not guts but the example of Robert Rauschenberg. His white paintings… when I saw those, I said, 'Oh yes, I must. Otherwise I'm lagging, otherwise music is lagging'." Cage's musical equivalent to the Rauschenberg paintings uses the "silence" of the piece as an aural "blank canvas" to reflect the dynamic flux of ambient sounds surrounding each performance; the music of the piece is natural sounds of the players, the audience, the building, and the outside environment.

Cage was not the first composer to conceive of a piece consisting solely of silence. One precedent is "In futurum", a movement from the Fünf Pittoresken for piano by Czech composer Erwin Schulhoff. Written in 1919, Schulhoff's meticulously notated composition is made up entirely of rests. Cage was, however, almost certainly unaware of Schulhoff's work. Another prior example is Alphonse Allais's Funeral March for the Obsequies of a Deaf Man, written in 1897, and consisting of nine blank measures. Allais's composition is arguably closer in spirit to Cage's work; Allais was an associate of Erik Satie, and given Cage's profound admiration for Satie, the possibility that Cage was inspired by the Funeral March is tempting. However, according to Cage himself, he was unaware of Allais's composition at the time (though he had heard of a 19th-century book that was completely blank).