stylistic:tone
1946–1953: Early career in Paris

On 12 February 1946, the pianist Yvette Grimaud gave the first public performances of Boulez's music (Douze Notations and Trois Psalmodies) at the Concerts du Triptyque. Boulez earned money by giving maths lessons to his landlord's son. He also played the ondes Martenot (an early electronic instrument), improvising accompaniments to radio dramas and occasionally deputising in the pit orchestra of the Folies Bergère. In October 1946, the actor and director Jean-Louis Barrault engaged him to play the ondes for a production of Hamlet for the new company he and his wife, Madeleine Renaud, had formed at the Théâtre Marigny. Boulez was soon appointed music director of the Compagnie Renaud-Barrault, a post he held for nine years. He arranged and conducted incidental music, mostly by composers whose music he disliked (such as Milhaud and Tchaikovsky), but it gave him the chance to work with professional musicians, while leaving time to compose during the day.

His involvement with the company also broadened his horizons: in 1947 they toured to Belgium and Switzerland ("absolutely pays de cocagne, my first discovery of the big world"); in 1948 they took Hamlet to the second Edinburgh International Festival; in 1951 they gave a season of plays in London, at the invitation of Laurence Olivier; and between 1950 and 1957 there were three tours to South America and two to North America. Much of the music he wrote for the company was lost after the occupation by students of the Théâtre de l'Odéon during the civil unrest in May 1968.

The period between 1947 and 1950 was one of intense compositional activity for Boulez. New works included the first two piano sonatas and initial versions of two cantatas on poems by René Char, Le Visage nuptial and Le Soleil des eaux. In October 1951, a substantial work for eighteen solo instruments, Polyphonie X, caused a scandal at its premiere at the Donaueschingen Festival, some audience members whistling and hissing during the performance.

Around this time, Boulez met two composers who were to be important influences: John Cage and Karlheinz Stockhausen. His friendship with Cage began in 1949 when Cage was visiting Paris. Cage introduced Boulez to two publishers (Heugel and Amphion) who agreed to take his recent pieces; Boulez helped to arrange a private performance of Cage's Sonatas and Interludes for Prepared Piano. When Cage returned to New York they began an intense, six-year correspondence about the future of music. Their friendship later cooled as Boulez could not accept Cage's increasing commitment to compositional procedures based on chance; he later broke off contact with him. In 1952 Stockhausen arrived in Paris to study with Messiaen. Although Boulez knew no German and Stockhausen no French, the rapport between them was instant: "A friend translated we gesticulated wildly... We talked about music all the time—in a way I've never talked about it with anyone else."

In July 1952, Boulez attended the International Summer Course for New Music in Darmstadt for the first time. As well as Stockhausen, Boulez was in contact there with other composers who would become significant figures in contemporary music, including Luciano Berio and Luigi Nono. Boulez quickly became one of the leaders of the post-war modernist movement in the arts. As the music critic Alex Ross observed: "at all times he seemed absolutely sure of what he was doing. Amid the confusion of postwar life, with so many truths discredited, his certitude was reassuring."