Mr. Ozawa, who underwent treatment for esophageal cancer in 2010, had been in fragile health for years. He was expected to conduct the Boston Symphony in July 2016 but pulled out that May because of what was described as a “lack of physical strength.”
It was a melancholy coda for a man who had arrived in Boston in the early 1970s a long-haired and fashionably clad maestro who exuded youthful energy and seemed a sharp contrast to the middle-aged, tuxedoed Northern Europeans who had long dominated the podium in classical music.
It was the twilight of the counterculture, Boston was booming, and Mr. Ozawa seemed at home in that most collegiate of college towns, newly awakened from a long period of being considered staid and hidebound. His studiously hip, turtle-necked, love-beaded image (adroitly advanced by the BSO’s public relations department) made him seem a new sort of music director for a new age.
Suddenly, Mr. Ozawa was everywhere: conducting the BSO as well as the Muppets’ all-animal orchestra on public television, gracing magazine covers, making appearances at Red Sox games as a high-profile ticket-holder. He won two Emmy Awards for his televised conducting and was the subject of a documentary co-directed by the Maysles Brothers.
Mr. Ozawa joined a tiny elect of classical musicians, among them Beverly Sills, Leonard Bernstein and Luciano Pavarotti, who were known not only to concert audiences but also to a vast general public.
Despite the onslaught of publicity, it was obvious from the beginning that Mr. Ozawa was a serious, thoughtful and prodigiously gifted musician. He dazzled orchestras and audiences with what the Pulitzer Prize-winning composer Leon Kirchner once called “the scent, the sense, the sensuality of an extraordinary person.” He attracted world-class mentors such as Bernstein of the New York Philharmonic and Herbert von Karajan of the Berlin Philharmonic.
Richard Dyer, the longtime Boston Globe music critic, wrote in 2002 that Mr. Ozawa “displayed the greatest physical gift for conducting of anyone in his generation, and a range and accuracy of musical memory that struck awe and envy into the hearts of most musicians who encountered it.”
He remained in later years, Dyer added, “beautiful to watch, and unique in the amount of focused information and emotion that he can communicate through glance, attitude, and gesture. Ozawa is calligraphy in motion, precise and evocative.”
Mr. Ozawa had a nearly unparalleled gift for uniting huge orchestras and choruses in long, complex and densely populated works, such as Hector Berlioz’s “Damnation de Faust,” Arnold Schoenberg’s “Gurre-Lieder,” Benjamin Britten’s War Requiem and Richard Strauss’s opera “Elektra,” which he presented in concert form with the BSO.
He led the world premiere of Olivier Messiaen’s four-and-a-half hour opera “Saint François d’Assise” (1983) at the Paris Opera; the score called for an orchestra of 150 and included 41 parts for percussion alone.
He recorded all of these works, as well as the complete symphonies of Ludwig van Beethoven, Johannes Brahms, Pyotr Ilyich Tchaikovsky and Gustav Mahler and hundreds of other pieces. Most of his discs were made with the BSO, but he also recorded with leading orchestras including Vienna and Tokyo.
But it is likely that his tenure in Boston — at 29 years, the longest music directorship in the orchestra’s history — will be his principal legacy. It was a legacy that became hotly debated as the years wore on. As his obligations mounted, many critics expressed dismay that Mr. Ozawa, once so exhilarating, seemed increasingly to coast on perfunctory and often artistically underwhelming performances. Morale plunged among the musicians.
He retained devoted fans and protectors who continued to bestow laurels on him, and he received the 2015 Kennedy Center Honors, which cited him as “one of the great figures of the classical music world today.” But there was relief when James Levine, the longtime music director of the Metropolitan Opera, took over Mr. Ozawa’s duties at the BSO.
By many accounts, Levine re-energized the BSO before his own health setbacks interfered with his demanding schedule. Mr. Ozawa was asked by the Globe whether he took the plaudits directed at Levine as a slap on his own tenure.
“No, no, no,” he said. “I don’t take personally. If he stayed 29 years like me. . . they know my weak point and I know theirs. Jimmy is a super-talented man. His music ability is very high and that helps the orchestra with new freshness. It’s natural. . . . It’s good for audience, too.”
Seiji Ozawa, the third of four siblings of a Buddhist father and Christian mother, was born on Sept. 1, 1935, in Mukden (now Shenyang), Manchuria, during the Japanese occupation of that region of China.
His father was there as a railroad company dentist, but his growing sympathy for the plight of the Chinese and his involvement with a pacifist organization led to conflicts. The Ozawas were soon deported back to the Japanese mainland.
His family settled in Tachikawa, the site of a military air base outside Tokyo. His father was denied a license to practice and scraped by as a rice farmer. Mr. Ozawa vividly recalled being drawn to music by the church hymns his mother sang around the home.
He soon began keyboard studies, immersing himself in Brahms, Beethoven and Johann Sebastian Bach with the intention of becoming a concert pianist, an ambition he abandoned in his teens after breaking both index fingers in a rugby game.
After his piano teacher told him to consider conducting, he went for the first time to hear a live symphony. Mr. Ozawa, then 14, said he found the performance a revelation: not the tinny and scratchy noise emanating from the radio or an old record player but a swirl of movement and power that provoked shivers in his body.
As Mr. Ozawa remembered it, his mother then wrote a letter to a distant relative of hers, the cellist, conductor and teacher Hideo Saito, who had been influential in the introduction of Western classical music to Japan and particularly to Japanese children.
Mr. Ozawa paid for his lessons at Saito’s Toho Gakuen School of Music in Tokyo by helping with orchestration and mowing the lawn. Emerging as the star pupil, he set off in 1959 to compete in an international competition for young conductors in Besançon, France, making the two-month voyage to Europe by cargo ship.
He won first place at Besançon and particularly impressed one of the jurors, Charles Munch, the music director of the Boston Symphony. Munch invited him to attend the Berkshire Music Center at Tanglewood, the BSO’s summer home in western Massachusetts, which had been founded in 1940 to foster young players and composers.
Mr. Ozawa took Tanglewood’s highest conducting honor in that summer of 1960, and Bernstein named him an assistant conductor with the New York Philharmonic beginning in the 1961-1962 season.
Bernstein’s influence on Mr. Ozawa was significant, not only in the physicality of their technique from the podium but also in their preference for modish dress and their similarly untamed hair, which they liked to sweep back with a hand amid a particularly vigorous performance.
Such habits did little to endear Mr. Ozawa to his countrymen when he returned to Japan in 1962 to conduct the country’s leading ensemble, the NHK Symphony Orchestra. Some older musicians refused to play for him, finding his manner too cocky and Westernized.
“To the Japanese, my talent had hatched too quickly,” he told the Globe years later. “I popped into prominence the way kernels become popcorn, fast. The orchestra members boycotted me. They said I had bad manners. It was true. They said I pushed them too hard. It was true. They said I was a bully. It was true. I thought it was just a matter of working hard. But management was on the side of the musicians.”
However, Mr. Ozawa continued to return to Japan for engagements while rapidly making his name in North America.
At 28, he became music director of the Chicago Symphony Orchestra’s summer seasons at the Ravinia Festival. In addition, he was named permanent conductor of the Toronto Symphony Orchestra in 1965 and of the San Francisco Symphony in 1970. Then Boston beckoned, with the chance to take the helm of one of the oldest and most prestigious orchestras in the United States.
He became the BSO musical adviser in 1972 and musical director the next year. By the end of the decade, as communist China began to reestablish cultural ties with the West, he accepted an invitation to conduct Beijing’s Central Philharmonic Orchestra in China. He also took the BSO on a tour of China, the first Western orchestra to undertake such an adventure.
In a wrenching decision in the late 1970s, Mr. Ozawa decided with his second wife, Vera Ilyan, whose heritage was Russian and Japanese, that she would return to Tokyo and raise their two children there, immersing them in the Japanese language and cultural values.
Yet he kept adding to his duties. In 1992, he established the Saito Kinen Festival in Matsumoto, Japan, naming what immediately became one of the world’s leading youth orchestras in honor of his teacher. As was customary with BSO music directors, he also served as director of the Tanglewood Music Festival, and, in 1994, Seiji Ozawa Hall opened on its western grounds. Much of the funding came from the company Sony: Mr. Ozawa was by now a national hero in Japan.
In 1997, Mr. Ozawa became a controversial figure at Tanglewood when he pushed out a popular administrator, Richard Ortner, over conflicts involving programming and training for the students. Many celebrated faculty members — among them pianists Leon Fleisher and Gilbert Kalish and bassist Julius Levine — left in protest.
Moreover, relations with the BSO were souring over his peripatetic workload, and what had once seemed a magical association with the orchestra appeared increasingly stale. The critical consensus was that he had stayed too long. “He still dances on the podium with his trademark pixie charm,” composer and critic Greg Sandow observed in the Wall Street Journal, “but he looks far better than his orchestra sounds.”
Mr. Ozawa resigned from the BSO in 2002 to become the music director of the Vienna State Opera, a position he held for eight years.
He and Ilyan had two children. His first marriage, to pianist Kyoko Edo, ended in divorce. A list of survivors was not immediately available.
Mr. Ozawa held dual Japanese-American citizenship and described his life and career as a successful, if not always perfectly smooth, melding of Eastern and Western culture and pride. “Western music is like the sun,” he told Time magazine in 1987. “All over the world, the sunset is different, but the beauty is the same.”