John Cage, the highly inventive, often perplexing avant-garde composer who theorized that music doesn't have to have sound but can be anything that fills a space in time, died Aug. 12 in New York. He was 79.

A spokeswoman for St. Vincent's Hospital in Manhattan said Cage died there after suffering a stroke at his home.

Described by the Encyclopaedia Brittanica as "a composer whose work and revolutionary ideas profoundly influenced mid-20th century music," Cage was a guru of modern sound who made voluminous and complicated tracks across the world of music as he defined his challenges to conventional musical wisdom.

He wrote 12-tone music in 1934, organized a percussion orchestra in 1938, composed for prepared piano (where objects are inserted between some of the piano's strings) in 1940 and used electrically produced sounds in 1942.

"I like ambient sound," he said in an interview last year. "I don't object to burglar alarms or hums from refrigerators."

In 1951, he scored a piece that included the noise from 12 radios. His first piece on magnetic tape came in 1952. At the end of that decade, he began writing scores leaving choices of sounds to the performers.

In 1962, Cage performed "O'O," in which he sliced vegetables, put them in a blender and drank the juice.

In the 1970s, he was turning astronomical charts into orchestral scores and computerized the "I Ching" into his first opera, "Europera," in the 1980s.

The Los Angeles-born composer liked to make each musical piece different.

"My father was an inventor. If I can, with each piece I make something like a discovery," Cage said.

He also wrote poetry and essays, lectured, painted and etched, played chess with masters and was considered an expert on mushrooms.

Cage's most popular work probably was "Sonatas and Interludes for Prepared Piano," which he wrote in the mid-1940s. In it, he had metallic objects placed among many of the instrument's strings to make it, in his words, "a percussion ensemble under the control of a single player."

His 1939 "The Imaginary Landscape No. 1" is considered by some to be the first electronic composition. The sounds were provided by test recordings of constant frequencies, the kind used by radio stations and in acoustical research. Two performers varied the frequencies by manipulating variable-speed turntables, switching stations and fluctuating the volume.

He became as well or better known for his persona than for his music.

His signature opus, "4'33," is four minutes and 33 seconds in which a pianist simply stepped onstage, sat at the piano in silence and then walked off to applause.

John Milton Cage Jr. studied piano and composition in Los Angeles and Paris, returning in the late 1930s to the United States, where he worked as a dance accompanist.

About that time, he developed a piano technique using tone clusters and playing directly on the strings. He studied counterpoint with Arnold Schoenberg at the University of California at Los Angeles, where Schoenberg told him he had no feeling for harmony.

His compositions from that period were based on a schematic organization of the 12 pitches of the chromatic scale.

In 1940, he settled in San Francisco and gave concerts of percussion music and then taught contemporary composition at the Chicago Institute of Design. Two years later, he settled in New York, which was to be his base for the remainder of his life.

Cage left no immediate survivors.