Pierre Boulez, 90; French composer

As a young composer — and throughout his life as an insistently private man — he matched intelligence with great force of mind: He knew what had to be done, according to his reading of history, and he did it, in defiance of all the norms of French musical culture at the time. His “Marteau Sans Maître” (“Hammer Without a Master”) was one of this pioneering group’s first major achievements, and it remains a landmark of modern music.

His influence was equally great on the podium. In time he began giving ever more attention to conducting, where his keen ear and rhythmic incisiveness could produce a startling clarity. (There are countless stories of him detecting faulty intonation, say, from the third oboe in a complex piece.)

He reached his peak as a conductor in the 1960s, when he began to appear with some of the world’s great orchestras, including the Concertgebouw in Amsterdam, the Berlin Philharmonic, and the Cleveland Orchestra. His style was unique. He never used the baton, but manipulated the orchestra by means of his two hands simultaneously, the left indicating phrasing or, in much contemporary music, counterrhythm.

His characteristic sound — unemotional on the surface but with undercurrents of intemperateness, at once brilliant in color and rhythmically disciplined — depended on his famously acute ear and suited his core repertoire: Stravinsky (several of whose works he introduced to Europe), Debussy, Webern, Bartok, and Messiaen.

To be a conductor, though, meant working with the existing machinery, and that was not something a revolutionary like Mr. Boulez was willing to do. So he tried to remake that machinery. After becoming music director of both the New York Philharmonic and the BBC Symphony Orchestra in London in 1971, he explores unconventional repertoire, unconventional concert formats, and unconventional locations.

But he also accepted that he had to rethink some of his own preconceptions, and as his musical outlook broadened, his output as a composer dwindled.

It was his reputation as an avant-garde composer and as a crusader for new music that prompted his unexpected appointment as music director of the New York Philharmonic, succeeding Leonard Bernstein. After the initial shock at his arrival, there was hope that he might, as many said at the time, bring the orchestra into the 20th century and appeal to younger audiences. But his programming often met with hostility in New York, and he left quietly six years later.

His destination was Paris. Dismissive of the French musical establishment, he had spent most of the previous two decades abroad, but President Georges Pompidou, keen to reclaim a native son, had agreed to found a contemporary-music center for him in the capital: the Institute for the Research and Coordination of Acoustics and Music. It had its own 31-piece orchestra, the Ensemble Intercontemporain. In the 1980s, he gained further government support for his grandest project, the City of Music complex in the Villette district of Paris, housing the Paris Conservatoire, a concert hall, and an instrument museum.

Pierre Boulez was born on March 26, 1925, in Montbrison, a town near Lyon, the son of an industrialist, Léon, and the former Marcelle Calabre. He began to compose in his teens.

A defining moment came when he heard a broadcast of Stravinsky’s “Song of the Nightingale”; it was a work to which he often returned throughout his conducting career. Against the wishes of his father, who wanted him to study engineering, he went to Paris in 1942 and enrolled at the Conservatoire.

In 1944-45, he took a harmony class taught by Olivier Messiaen, whose impact on him was decisive. Messiaen’s teaching went far beyond traditional harmony to embrace new music that was outlawed both by the stagnant Conservatoire of that period and by the German occupying forces: the music of Schoenberg, Stravinsky, Bartok, and Webern. Messiaen also introduced his students to medieval music and the music of Asia and Africa. Mr. Boulez felt his course was set; but he also knew he needed to go further into the 12-tone method that Schoenberg had introduced a generation before.

“I had to learn about that music, to find out how it was made,” he once told Opera News. “It was a revelation — a music for our time, a language with unlimited possibilities. No other language was possible. It was the most radical revolution since Monteverdi. Suddenly, all our familiar notions were abolished. Music moved out of the world of Newton and into the world of Einstein.”

Soon, in such works as his mighty Second Piano Sonata (1947-48), he was integrating what had been separate paths of development in the music of the previous 40 years: Schoenberg’s serialism with Stravinsky’s rhythmic innovations and Messiaen’s enlarged notion of mode. As he saw it, all these composers had failed to pursue their most radical impulses, and it fell to a new generation — specifically, to him — to pick up the torch.

Boulez made his debut as a concert conductor on March 21, 1956, at a Domaine Musical concert. The program included “Le Marteau Sans Maître.” At once delectable and stringent, this work united traditions of Austrian-German discipline and French finesse with the sounds of Africa, East Asia, and South America, made available by its variegated ensemble (including alto flute, viola, guitar, and percussion besides contralto voice). It was widely admired, not least by Stravinsky, who heard it when Mr. Boulez made his North American debut in Los Angeles a year later.

Mr. Boulez then began a lasting connection with the Southwest German Radio Symphony Orchestra of Baden-Baden, where he made his home.

A musical work should be, Mr. Boulez often said, a labyrinth, with no fixed route. It might also never gain a fixed ending. He began starting more works than he ever brought to completion, while at the same time submitting older pieces to rounds of revision.

As a conductor, he showed much less hesitation. Where his first concerts had been devoted entirely to 20th-century works, he began to explore earlier repertoires — Haydn, Bach, Schubert, Mozart, Beethoven — with the Concertgebouw and the Southwest German Radio Symphony Orchestra in the early 1960s. In March 1965, he made his debut with a US orchestra, the Cleveland Orchestra, in a typical program comprising Rameau, his own music (“Figures-Doubles-Prismes”), Debussy, and Stravinsky (“The Song of the Nightingale”).

His appointment to the New York Philharmonic in 1971 presented great challenges. As music director he had to enlarge his repertoire rapidly. Until then he had conducted very little Romantic music.

Both his programming and his handling of an older repertoire met with some resistance from audiences, critics and, it was said, even some of his musicians. Harold C. Schonberg of The New York Times called Mr. Boulez “a brainy orchestral technician” whose “scientific approach” lacked heart. Reviewing a 1972 concert that included Edgard Varèse’s 1927 composition “Arcana,” Donal Henahan of The Times reported that “perhaps a quarter of the downstairs audience” at Philharmonic Hall “fled as if from the Black Death” before the piece was performed.

Mr. Boulez wanted to make the orchestra a more flexible institution, and a more modern one. Performances might begin with short programs of chamber music, played by members of the orchestra.

Later in his career, he began to appear more widely again as a conductor, with orchestras in the United States (Los Angeles, Cleveland, Chicago) and Europe. At his death, he was the conductor emeritus of the Chicago Symphony Orchestra.

Among the honors he received in his later years were the Kyoto Prize in 2009 and dozens of Grammy Awards.