In 1948, Takemitsu conceived the idea of electronic music technology, or in his own words, to "bring noise into tempered musical tones inside a busy small tube." During the 1950s, Takemitsu had learned that in 1948 "a French [engineer] Pierre Schaeffer invented the method(s) of musique concrete based on the same idea as mine. I was pleased with this coincidence."  In 1951, Takemitsu was a founding member of the anti-academic Jikken Kobo (Shi Yan Gong Fang , "experimental workshop"): an artistic group established for multidisciplinary collaboration on mixed-media projects, who sought to avoid Japanese artistic tradition. The performances and works undertaken by the group introduced several contemporary Western composers to Japanese audiences. During this period he wrote Saegirarenai Kyusoku I ("Uninterrupted Rest I", 1952: a piano work, without a regular rhythmic pulse or barlines); and by 1955 Takemitsu had begun to use electronic tape-recording techniques in such works as Relief Statique (1955) and Vocalism A*I (1956). Takemitsu also studied in the early 1950s with the composer Fumio Hayasaka, perhaps best known for the scores he wrote for films by Kenji Mizoguchi and Akira Kurosawa, the latter of whom Takemitsu would collaborate with decades later.  In the late 1950s chance brought Takemitsu international attention: his Requiem for string orchestra (1957  listen ), written as an homage to Hayasaka, was heard by Igor Stravinsky in 1958 during his visit to Japan. (The NHK had organised opportunities for Stravinsky to listen to some of the latest Japanese music; when Takemitsu's work was put on by mistake, Stravinsky insisted on hearing it to the end.) At a press conference later, Stravinsky expressed his admiration for the work, praising its "sincerity" and "passionate" writing. Stravinsky subsequently invited Takemitsu to lunch; and for Takemitsu this was an "unforgettable" experience. After Stravinsky returned to the U.S., Takemitsu soon received a commission for a new work from the Koussevitsky Foundation which, he assumed, had come as a suggestion from Stravinsky to Aaron Copland. For this he composed Dorian Horizon, (1966), which was premiered by the San Francisco Symphony Orchestra, conducted by Copland.

Answer this question "what year did the early development start?" by extracting the answer from the text above.
In 1948, Takemitsu conceived the idea of electronic music technology, or in his own words, to "bring noise into tempered musical tones inside a busy small tube.