BERKELEY, Calif. — “I have to apologize,” the composer John Adams said as he approached his car. “The front seat was torn up by a bear.”Patches of the passenger seat were slashed open, revealing the stuffing inside. Bears aren’t a hazard in the hilly neighborhoods of “the People’s Republic of Berkeley,” as Adams wryly referred to his town, but they are in the Sierra Nevada, where he sometimes retreats to work at his cabin.One night, while Adams was in the mountains with his dog, Amos, beer exploded in the car’s trunk because of the altitude, and a bear wreaked havoc trying to get a taste. “It’s probably a problem that Stravinsky didn’t have,” he said.Adams and Stravinsky might not have that in common, but they share much else: a recognizable yet constantly evolving musical language; a body of work across a wide breadth of genres and forms; and, above all, something close to supremacy in the classical music of their time. And, at 75 — the same age as Stravinsky when he took a stylistic turn for his late masterpiece “Agon” — Adams is making a swerve with his latest opera, “Antony and Cleopatra,” which premieres at San Francisco Opera on Sept. 10 ahead of future productions, including at the Metropolitan Opera in New York.There is an easy argument to be made that Adams is the greatest living American composer. He is an artist for whom Americanness truly matters, as much as the tradition of Western classical music — both heritages treated not with nostalgia, but with awareness and affection. Whose DNA carries traces of Beethoven and Ellington, Claude Debussy and Cole Porter. Whom younger composers regard with a mixture of awe and fondness, and who, in turn, is quick to give advice and life lessons. And who has made opera, as the singer Gerald Finley said, “a force for social commentary.”That corner of Adams’s output, which began in 1987 with “Nixon in China,” has never been mere art for art’s sake. “Nixon” — an essential American opera of the last 50 years, along with Meredith Monk’s “Atlas” and Philip Glass’s “Satyagraha” — made myth of recent history. Even more immediate was “The Death of Klinghoffer” (1991), an account of the Achille Lauro hijacking, which had happened just six years earlier. “Doctor Atomic,” from 2005, reached farther back to meditate on J. Robert Oppenheimer and the Manhattan Project; and in 2017, “Girls of the Golden West” revisited a 19th-century California with eerily coincidental connections to the Trump era.“Doctor Atomic” had its Metropolitan Opera premiere in 2008. Suzanne DeChillo/The New York Times“Nixon in China,” Adams’s first opera, at the Met in 2011.Sara Krulwich/The New York TimesAdams has brought contemporary politics “into the cultural sphere,” said Finley, the bass-baritone who originated the role of Oppenheimer, and opened discussion “about the role of opera and music in society, and who we are as people.”As the classical music world celebrates Adams’s 75th year — not least with a new 40-disc box set of collected works from the Nonesuch label — and San Francisco Opera (itself marking a milestone of 100 seasons) prepares for the premiere of “Antony and Cleopatra,” he was understandably anxious during a recent hike in Tilden Regional Park.He followed a ridge trail that, to the left, revealed a vista of the foggy San Francisco Bay, with the peak of Mount Tamalpais in Marin County emerging from the clouds, and, to the right, sun-streaked hills and valleys leading to the distant Sierras. In between pointing out a bunny or sharing a story about Amos and coyotes, he — a composer who cares about public reception and reviews — said that while the new opera was at least obliquely relevant, in the way that Shakespeare tends to be, he worried people would be expecting something like “Nixon.”“When you get to be my age, you’re not compared to other composers,” he said. “You’re compared to your earlier works.”COULD ADAMS BE ANYTHING other than a deeply American composer? “Not with my name,” he said with a chuckle. But that name — John Coolidge Adams — “so blue-bloodedly Yankee in its import,” he wrote in his 2008 memoir, “Hallelujah Junction,” “was in fact a conjunction of a Swedish paternal grandfather and a maternal grandfather I never knew.”Born in Massachusetts and raised around New England, with a singer for a mother and clarinetist for a father, he grew up around big band music and the Great American Songbook alongside symphonic classics. On the family turntable he listened to Tchaikovsky’s “1812 Overture” and an album called “Bozo the Clown Conducts Favorite Circus Marches,” conducting along with a knitting needle.Adams with music for “Antony and Cleopatra” at his longtime home in Berkeley, Calif.Marissa Leshnov for The New York TimesBy adolescence he aspired to composing, while playing clarinet and formally learning to conduct. During one formative summer, he saw the film adaptation of “West Side Story.” “It was the moment,” he wrote in his memoir, “when I felt most aroused to the potential of becoming an artist who might forge a language, Whitman-like, out of the compost of American life.”That did not come easily during his years at Harvard University, where he studied with teachers including Leon Kirchner, David Del Tredici and Roger Sessions, in the spirit of the mid-20th century high modernism that was fashionable around composers of the Darmstadt School. On the side, Adams continued with the clarinet, subbing at the Boston Symphony Orchestra, including at the American premiere of Schoenberg’s “Moses und Aron.” Aaron Copland, Adams wrote, once heard him play and remarked, “Yeah, the kid knows his stuff.”After college, Adams moved to the Bay Area — his first views of the untamed California coast later found their way into “The Dharma at Big Sur” (2003) — and took a teaching job while programming concerts packed with works by avant-gardists like John Cage, Robert Ashley and Ingram Marshall. He also toiled away at electronic music, blending it with acoustic sounds in “American Standard,” from 1973; the middle movement, “Christian Zeal and Activity,” stretches a hymn melody to glacial beauty alongside, on Edo de Waart’s recording with the San Francisco Symphony, a looping sermon.“Phrygian Gates,” a Minimalist yet sprawling piano solo from 1977, is Adams’s first mature work. More accomplishments quickly followed, like “Shaker Loops” and the chronically underrated “Common Tones in Simple Time” — which, he wrote in his memoir, summed up the goals of Minimalism in its title alone, and served as a farewell to the “chaste, scaled-down aesthetics of that particular style.”He wasn’t long for the Minimalism of Glass and Steve Reich, two composers a decade older than him. “I felt that in obeying that kind of rigor, there wasn’t a lot of potential for not only emotional surprise and emotional expression, but also formal flexibility,” Adams said. “I wanted to make a music that had potential for surprise, because that’s always what we’re looking for in any kind of artistic experience.”You can hear, in Adams’s strain of Minimalism, a harmonic language that grabs listeners by the heart, and a gift for layering lyricism with the style’s trademark pulses, as in “Harmonium” (1981). Robert Hurwitz, the longtime president of Nonesuch — who brought Adams to the label and created the new box set — said that while Glass and Reich “looked at music a different way,” Adams was continuing the path of music in the 20th century.“I think whether or not he was influenced at different points by Steve and Phil,” Hurwitz added, “he passed through those in the way that Picasso passed through Cubism or Stravinsky passed through Neo-Classicism. He is of the moment, and yet his music is always his own.”Adams was most brazenly idiosyncratic, and surprising, in his 1982 work “Grand Pianola Music,” which begins in comfortable, Minimalist territory before giving way to a cascading excess and a sweeping melody both familiar and unplaceable. The piece left early listeners perplexed — or angry at what they perceived as a thumbed nose at the hyperseriousness of modernism. It wasn’t a joke, though: It was a glimpse of a more honest voice in the making, one that would bloom with the symphonic “Harmonielehre” and “Nixon.”Adams also diverged from other Minimalists in his medium: At the time, they largely operated outside institutions, writing for their own ensembles and performing in lofts and galleries. But Adams’s music was popular among orchestras and institutions, and he brought Minimalism to the concert hall in the process.“The thing that he did is, I think, the hardest thing to do,” said the composer Nico Muhly. “Which is to take the influences of — let’s pretend that it’s a kind of American Minimal tradition — and the time space that you find in Wagner, and figure out how to make those things live next to each other, to work together.”As Adams’s more personal style developed, it carried traces of the Western classical tradition — with the colorist acuity of Debussy and the American vernacular of Ives and jazz — in a way that could be mistakenly labeled postmodern but isn’t. The composer Dylan Mattingly said that Adams brings an element of the familiar into his work with sincerity because “John just loves that music, and so he’s interested in writing music that uses the instrument of the orchestra, while still being totally revolutionary and totally exploratory.”Whiffs of popular idioms in, say, “The Chairman Dances” (1985) were a clear break from the Darmstadt School brand of modernism that had dominated Adams’s youth — the music of composers like Pierre Boulez and Karlheinz Stockhausen — but had begun to be overtaken by Minimalism and a broader return to tonality. And it coincided with what Adams called “one of my Saul on the road to Damascus moments,” when he started reading Dickens novels in his 30s.“The first thing that struck me was that there was a person making great art,” Adams recalled. “I mean, sometimes terrible, sappy sentimentalism, but you turn the page as fast as you can. And, like Tolstoy or Victor Hugo, he was writing important work with social connections or social influence. They had enormous audiences. I thought about our time; we composers have sort of surrendered that to pop music.”A pop star Adams isn’t, but he is one of the few composers who approaches that status, second only, perhaps, to Glass. And from that perch he has, in the vein of his literary heroes, written music of conscience and consequence. Alongside exercises in form and timbre, like the Violin Concerto (1994) and, more recently, “Must the Devil Have All the Good Tunes?” (2019), have been “On the Transmigration of Souls,” Adams’s Pulitzer Prize-winning response to the Sept. 11 attacks, and collaborations with the director Peter Sellars that explored contemporary social issues through classic lenses: “El Niño” (2000), a Christmas oratorio with the mastery of Handel’s “Messiah,” or the “The Gospel According to the Other Mary,” a retelling of the Passion from 2012.Davóne Tines and Julia Bullock in “Girls of the Golden West” at San Francisco Opera in 2017.Cory Weaver/San Francisco OperaAlong the way, Adams has also provided an invaluable service to the next generations of composers. He doesn’t teach, but he curates concerts, championing younger artists, some of whom he has helped as a mentor, like Mattingly and his peer Gabriella Smith, who said, “I hardly know any composers who have not been influenced by his music.”Adams is known to look at scores and give frank, productive feedback, but also lessons applicable beyond the work at hand. Smith described their time together as “more like hanging out,” but also a confirmation that her two biggest interests — music and nature — could coexist, as they do in Adams’s life. He got her thinking, she said, “about what it would be like to have my own, unique compositional voice.”Mattingly said that Adams once responded to a piece of his by pulling out a Mahler score and talking about the physicality of it. Mattingly eventually realized the conversation was about how music could be embodied. Adams was pushing him to think about “music as the amorphous, invisible thing that it actually is,” Mattingly said, “instead of as specific durations and straight lines. I remember thinking about it nonstop for months, and then creating something that was way more compelling afterward.”“THE MOST TEDIOUS THING an artist can do,” Adams said, “is brand himself or herself.” If there’s a genre in which this most applies to him, it’s opera. Although all his stage works are on some level political, they occupy distinct sound worlds. In “Nixon,” created with the librettist Alice Goodman and Sellars, the mode was, Adams wrote in his memoir, “Technicolor orchestration.” But when the team reunited for “Klinghoffer” — their triumph, though, as a magnet for controversy over the Israeli-Palestinian conflict, one that is virtually impossible to produce in the United States — the text called for “something that was intensely poignant and lyrical, but also violent,” Adams said.Adams and Sellars assembled the libretto for “Atomic” from found texts. Critics called the result of their method undramatic, but the work has been increasingly accepted in recent years, in part because of a 2018 recording that, with the soprano Julia Bullock as Kitty Oppenheimer, brought the dramaturgy more into focus. Such a turnaround has yet to come for “Girls of the Golden West,” whose libretto had few fans, despite a lean, focused score that will have its moment in the sun when the Los Angeles Philharmonic presents it in concert in January.John Adams with his dog, Amos, in Tilden Regional Park, where they take daily walks.Marissa Leshnov for The New York Times“Antony and Cleopatra” is a departure in more ways than one. Its libretto is almost entirely chipped from the Shakespeare original, in collaboration with Lucia Scheckner and Elkhanah Pulitzer, who is directing the premiere in San Francisco. And as such, it is a work of written-through drama, rarely pausing for reflection and moving propulsively toward its tragic climax.The title roles were written with Finley and Bullock in mind (along with Paul Appleby, another Adams veteran, as Caesar); Bullock, though, is pregnant and withdrew from the San Francisco run, so Cleopatra will be sung by Amina Edris. During recent rehearsals, the orchestra and cast were settling into the score, whose breakneck pace is set from the start by “archetypal” rhythms, Adams said, that may remind listeners of Beethoven’s Ninth Symphony or Wagner’s Nibelheim music from “Das Rheingold.” The vocal writing, meanwhile, largely follows the pace of speech like Debussy in “Pelléas et Mélisande,” or Janacek in his operas.“He really went from the words,” said Eun Sun Kim, the opera company’s music director, who is conducting the run. “It’s really about storytelling, but he also challenges us to be precise and at the same time musical.”As in Adams’s partnership with Sellars, the production’s concept seems conceived alongside the development of both the libretto and score. Pulitzer said that their entry point was “manifestations of Cleopatra, mostly through the lens of Hollywood, whether it’s Liz Taylor winking at the camera or the de Mille ‘Cleopatra’ integrating glamour and ancient Egypt.” That led them to the idea of movie palaces and news reels, which were then woven into the show.The approach is one way to bring the opera’s themes to the fore — principally, its depiction of one nation’s fall and the rise of another. “We all worry that America is in decline with Donald Trump and this horrible polarization,” Adams said. “I thought the dichotomy between Rome, which is ascendant, and Egypt, which is in decline, is very much a contemporary topic.”During the hike in Tilden, Adams followed a lot of reflections on the new opera with a “we’ll see.” Unsure of what audiences will think of it, he also doesn’t know what a success now would mean for the future. “I keep a mental picture of Meyerbeer,” he said, referring to the once ubiquitous and now rarely heard 19th-century composer, “just to remind myself: Here today, gone tomorrow.”He brought up about a performance that he conducted recently, of Bartok’s Music for Strings, Percussion and Celesta, with the Juilliard Orchestra. At one point, near the end, he got “this absolute chill running up my back.”“A chill is not the right word, because it was warm,” he continued. “It was just the feeling having a genuine, deep experience with a great creation. I know that it’s impossible not to sound trite, but that’s something that makes life and culture worth it. So, if somebody has an experience like that at some point from a piece of mine, then that’s all I really care about.” More