After facing anger during a prolonged labor dispute, the Met Opera’s music director has returned to the podium, emphasizing new work.The set for “Porgy and Bess” had been pushed to the back of the Metropolitan Opera’s stage on a recent Wednesday morning, and in front, lines of chairs and music stands had been set up. The company’s orchestra and chorus were coming together for the first time with the cast of “Eurydice” — a recent adaptation of Sarah Ruhl’s wistful play, with music by Matthew Aucoin — to run through the score in what’s known as a sitzprobe.Inside the vast and almost empty Met auditorium, Peter Gelb, the company’s general manager, typed on his laptop near the back of the theater. Ruhl was in the house; Mary Zimmerman, the director of the production, which opens on Tuesday, watched, too. Aucoin dashed around, listening for balances.At breaks, he rushed down the aisle to the pit to confer with the leader of any sitzprobe: the conductor. Here that was Yannick Nézet-Séguin, the Met’s music director, who offered the ensemble bits of counsel, sometimes asking for delicacy and transparency (“more French in approach”), sometimes for lyricism (“violas and cellos, you could sing a bit more”).The orchestra flew through one breathless passage in the second act, making a gallop to the final burst. “Ecstatic and chaotic,” said Nézet-Séguin, 46, smiling from the podium. “Is this something we can do?”With the New York Philharmonic’s director a newly declared lame duck, Nézet-Séguin is entering an era as the city’s presiding conductor, the one whose artistic achievements blur into civic stature.Jingyu Lin for The New York TimesChaos has lately dominated: The pandemic shut the Met for a year and a half. During much of that period, its unionized employees — including orchestra musicians and choristers — were furloughed without pay as a stalemate over compensation cuts dragged on.But the response to the company’s return has been ecstatic. And at the center of it all — short and muscular, with close-cropped, bleached-blond hair and a taste for rehearsal athleisure — is Nézet-Séguin. Omnipresent and energetic, he has been one of the central figures in New York’s cultural re-emergence, and certainly the city’s most significant and visible classical musician at a transformative moment.Over Labor Day weekend, shortly after the Met reached a deal with its unions, he conducted Mahler’s “Resurrection” Symphony — the first notes the company had played together since March 2020 — in front of thousands outside the opera house. Audiences soon returned inside the theater to hear him lead a nationally telecast performance of Verdi’s Requiem, for the 20th anniversary of Sept. 11.Later that month, he began the Met’s season in earnest at the podium for Terence Blanchard and Kasi Lemmons’s “Fire Shut Up in My Bones,” from 2019, the company’s first work by a Black composer. Nine days after that, he reopened Carnegie Hall with the Philadelphia Orchestra, of which he is also the music director, in the first of an astonishing nine dates for him at Carnegie this season. With the New York Philharmonic’s director, Jaap van Zweden, a newly declared lame duck, Nézet-Séguin is entering an era as the city’s presiding conductor, the one whose artistic achievements blur into civic stature.At the Met, he works from the ground-floor office once occupied by James Levine, who ruled the company for decades before being brought down by illness and allegations of sexual misconduct. Those troubles led Nézet-Séguin to ascend to the music directorship in 2018, two years ahead of schedule. Levine — who rarely led contemporary operas, let alone two in two months — died in March.When the Met’s unionized workforce was furloughed during the pandemic, some employees were angry that Nézet-Séguin was not earlier and louder in support.Jingyu Lin for The New York TimesThere has been a major change to the office. At the start of a recent interview there, Nézet-Séguin mimed tearing down a set of bookshelves that had blocked the view of Damrosch Park.“It feels symbolic,” he said. “It is to me. It’s about windows open and the fresh air of our repertoire and approach.”Despite the bright new light and the celebratory spirit of the past month and a half, the pandemic has been a dark period for Nézet-Séguin. During labor struggles, a music director’s position — closely connected to the players, but at the same time part of the administration — is intensely uncomfortable. There were musicians angry that Nézet-Séguin, who did not comment publicly on the negotiations until March, just after the orchestra agreed to begin accepting partial pay, was not earlier and louder in support.“It is a position that is unenviable,” Gelb said in an interview. “And one I hated to see him in. I’m used to catching fire during these disputes, and I hated to see him get it, too. I tried to keep him out of it; it was unfair for him to be in the middle of it. But I was not very good at protecting him.”The experience was unsettling for an artist whose rise to the top of his profession has been swift and sunny, and who is unused to hostility from musicians. (They tend to venerate him: “He’s the greatest conductor I’ve ever worked with,” said Harold Robinson, who is retiring as the Philadelphia Orchestra’s principal bass after 26 years.)“I didn’t know what to expect coming in,” Nézet-Séguin said of the orchestra’s first rehearsal after the furlough ended. “I said very little at the beginning. I said: ‘We lost many people. We lost members of our company. We lost people in our families, our friends.’ And the first notes were Verdi, actually. We just played it through. Let’s put all our emotions in this. And it helped.”Nézet-Séguin leading a rehearsal for the Met premiere of Matthew Aucoin and Sarah Ruhl’s “Eurydice.”Jonathan Tichler/Metropolitan OperaDavid Krauss, the Met’s principal trumpet, said in an interview: “There was some tension in the first half of the first rehearsal back. And by the second half, it was back to business as usual.”Not exactly business as usual. The pandemic, and the calls for racial justice that flared last year, fast-tracked the Met premiere of “Fire Shut Up in My Bones,” giving it pride of place on one of the highest-profile opening nights in the company’s history. The piece’s success — reviews were positive, four of the eight performances sold out, and the crowds were markedly more diverse than usual — has convinced Nézet-Séguin that works representing the experience of groups often marginalized in the classical canon, including Latinos and L.G.B.T. people, should be fixtures going forward.“This is showing us what we need to do,” he said, “and confirming what I’ve been wanting from Day 1.”But one question is whether, without the burst of publicity that accompanied the Met’s belated presentation of a Black composer’s work, new operas can hold their own at the box office. (To be fair, even classics have struggled to sell in recent years.) Test cases will come: While Nézet-Séguin has his eye on little-done corners of the repertory — he mentioned Gluck, Weber’s “Der Freischütz,” Korngold’s “Die Tote Stadt” and Ponchielli’s “La Gioconda” — he has decided that if the choice is between a rarity’s revival and a contemporary piece, the latter will get priority.“It should be at the expense, maybe, of some stuff I had wanted to bring back,” he said.“I had a lot of new pieces planned in the future,” Nézet-Séguin said. “But I was maybe thinking I would do one a year, or skipping some years. And now, no.”Jingyu Lin for The New York Times“We are reassessing all the operas I am going to be conducting,” he added, “because I don’t want this to be the exception, to do ‘Eurydice’ and ‘Fire.’ For me, this should be the norm. I had a lot of new pieces planned in the future. But I was maybe thinking I would do one a year, or skipping some years. And now, no.”Aucoin, the composer of “Eurydice,” said that Nézet-Séguin is a collaborator “to a degree that’s unusual for conductors.”“In the chaotic dance scene in Act I,” he added, “there’s this techno-esque line in the background, and my idea was that it should be only in the very bottom octave, the piano’s left hand and contrabassoons. I wanted it to be a pop song heard from another room. But it wasn’t registering. And he suggested we throw some bass trombone in there, and he was right.”On an early November afternoon in Philadelphia, Nézet-Séguin and his orchestra there presented an installment in the cycle of Beethoven symphonies they are also playing at Carnegie this season.Beethoven’s Second and Eighth framed “Sermon,” a suite of arias and spoken texts about race and struggle organized and performed by the young bass-baritone Davóne Tines. At its center is the calm, luminous sorrow of “Vigil,” written by Igee Dieudonné and Tines in memory of Breonna Taylor.New music can often feel randomly scattered onto an orchestral concert, added merely to give a progressive sheen to fundamentally conservative programming. But the mournful “Sermon” felt at home among the symphonies, both complementing and in tension with them, particularly as they were played by the Philadelphians with such graceful, sweet-not-saccharine polish and élan. Old and new, life and death, coexisted and enhanced one another.“That was the idea,” Nézet-Séguin said of Tines’s piece. “Giving him the space to tell us his story. I’m not a private, private person. I like to speak with you about my art; I like to go on television and share who I am as a person. But it’s not about me becoming more famous so that people give me attention. I’m not shying away from attention, but I want it to be helping the collective. I want to be the person who can help shed light on others.”“I’m not shying away from attention, but I want it to be helping the collective. I want to be the person who can help shed light on others.”Jingyu Lin for The New York TimesAt the end of February, Nézet-Séguin will achieve another repertory milestone at the Met, bringing Verdi’s “Don Carlos” there for the first time in its original French — rather than in the more common Italian, as “Don Carlo.” A few weeks later, as part of what is intended to be an ongoing collaboration between his two American institutions — he also leads the Orchestre Métropolitain of Montreal — he and the Philadelphia Orchestra will give the world premiere of Kevin Puts and Greg Pierce’s opera adaptation of “The Hours” in concert, before it is staged at the Met in a future season.The rebuilding of the Met is far from over. Eleven of its orchestra’s 96 regular full-time members retired or left their jobs during the pandemic. Should all be replaced? In what order? That is for Nézet-Séguin, in large part, to decide. And the company’s financial model, which keeps forcing the need for cuts and brinkmanship with the unions, is no closer to being permanently solved.“I can’t say we’re completely behind what happened last year,” Nézet-Séguin said. “We’re not. But at least these moments — this Verdi, this ‘Fire’ and now this ‘Eurydice’ — are helping everyone focus on what matters to us and how we can function together. And making a difference. It sounds cliché, but trying to make a difference in the world.”