It’s not that John Kander wasn’t touched by John Kander Day. The composer of the song “New York, New York” — played at every Yankees home game and known worldwide from its first five notes — was obviously moved when the city’s mayor handed him a framed proclamation in front of the St. James Theater in Midtown Manhattan. Nor was he jaded, he later said, about having that block of West 44th Street, from Broadway to Eighth Avenue, christened Kander & Ebb Way in recognition of his work and that of Fred Ebb, his longtime lyricist, who died in 2004.Still, of Kander’s thousands of songs, seven movie scores and 20 major musicals, including “Chicago” and “Cabaret,” not one bar was written with the idea of getting a piece of pavement named for him. If Ebb, with his brasher, needier personality, would have eaten up the honor, Kander seems at best to withstand it, embarrassed by too much attention or praise. He is so militantly unassuming that the highest compliment he will pay himself is the one his mother used to offer: “A horse can’t do any better.”So on March 24, as a choir sang and a crowd cheered and his friend Lin-Manuel Miranda read Ebb’s beautiful lyric for the song “First You Dream,” Kander, who had turned 96 days earlier, was thinking less about what was going on outside the St. James than what was going on inside it. There, a few hours after the ceremony, his 16th new Broadway musical, “New York, New York” — named for “that song,” which he doesn’t even like — would offer its first public preview. Directed and choreographed by Susan Stroman, it is set to open on April 26.Anna Uzele, center, as a singer whose troubled romance with a musician is one of the many stories told in the musical “New York, New York,” at the St. James Theater.Sara Krulwich/The New York TimesThough the plot is only tangentially related to that of the 1977 Martin Scorsese film starring Robert De Niro and Liza Minnelli, the stage musical, with a book by David Thompson and Sharon Washington, naturally includes its big numbers. Others are from the Kander and Ebb trunk, some never previously performed onstage. But much of the score is new. Six songs are collaborations with Miranda, who said the problem with writing lyrics for Kander is “just keeping up” as the melodies pour out, sometimes via voice memo at 3 in the morning. The rest, whether swingy or Schuberty or uncategorizable, are by Kander alone.At an age when most artists are resting on their laurels, or beneath them, Kander, the last of the great Golden Age composers, just keeps going. Other than arthritis in his hands, he is unimpaired physically; he trots up and down the three-story spiral staircase to his studio faster than I dared when I spent a few hours there with him. To the annoyance of his husband, Albert Stephenson, and everyone around him, he eats dessert regularly and generously, with no ill effect. “I do my chores, too,” he said: washing the dishes and making the bed, tight as a drum, as he was taught at Camp Nebagamon when he was 10.Well, lots of people remain spry seemingly forever. What worries artists, and especially composers, is the possibility of drying up creatively. Even musical theater titans like Rodgers and Berlin succumbed to harmonic meekness and rhythmic sclerosis as they approached their 70s. Certainly after Ebb’s death, and after fulfilling a promise to shepherd as many of the team’s unfinished musicals to Broadway as he could — “Curtains” in 2007, “The Scottsboro Boys” in 2010 and “The Visit” in 2015 — Kander might have been expected to coast into retirement on tributes and revivals.But no: Even before that job was finished, he’d jumped back into the water. In 2013 came “The Landing,” in 2017, “Kid Victory,” and in 2018 a dance play based on the Henry James novella “The Beast in the Jungle.” All three pieces, produced Off Broadway at the Vineyard Theater, were experimental in a way you might expect from someone at the start of a career, not seven decades into it. And now, even as “New York, New York” opens, another show is aborning.Kander and the lyricist Fred Ebb in 1987. Their 45-year partnership yielded works like “Cabaret” and “Chicago,” and was more intense and monogamous than many marriages.So it seems almost Sisyphean that while a music assistant is busy digitizing Kander’s archive and preparing the paper assets for eventual donation to the New York Public Library for the Performing Arts, the man himself is sitting nearby at a keyboard, cranking out more every day.That’s not the right phrase, though. Even if he were in fact profoundly lazy, as Ebb insisted and Kander does not deny, composing is hardly drudgery for him. It’s more of a geological process, water rising from an aquifer, desperate to be tapped. If he doesn’t let the music out through his hands — or block it by listening to somebody else’s — it might drown him.Which means he is always listening: Music plays in his head, he said, “like a radio you can’t turn off.” It began, he believes, some 35,000 John Kander Days ago, when, as a baby in Kansas City, Mo., he contracted tuberculosis. Isolated on a sleeping porch and able to sense his family only when they approached the screen door, he learned to associate the sound of footsteps coming toward him with the imminence of loved ones. “I think I began to organize sound in my head then, out of necessity.”FOOTSTEPS GO BOTH WAYS though. If, as he said, a “residue of loneliness” remains from that experience, it’s a loneliness for which “the most fortunate antidote” has been companionship and collaboration. Though many people assumed that Kander and Ebb were a couple — their 45-year partnership was more intense and monogamous than many marriages — the men were not socially close. But he and Stephenson, a dancer in Kander and Ebb’s “The Act,” have been together since 1977, married since 2008. Some of Kander’s loveliest songs were written not for any show but for him.As for collaboration, it’s no accident that Kander surrounds himself with a rotating roster of familiar names. “Next to the greatest sex you can imagine, making art with your friends is as good as it gets,” he said. He’s worked with Stroman six times, Thompson eight times and Washington, a featured performer in “The Scottsboro Boys,” twice. Half the music team are old Kander hands too, making the March 14 sitzprobe — the first rehearsal with the cast and the orchestra — a reunion and, as it happened, a party. You haven’t really heard “Happy Birthday” until a Broadway chorus of 37, accompanied by 19 crack musicians, sings it in a crowded, reverberant room.“There are a lot of really gorgeous places to be on this earth,” Kander told them, “but none as gorgeous as this.”Kander in his apartment with a 1963 painting by Camille Norman. The painting, depicting a scene from “Cabaret,” was given to him as a gift on the show’s opening night in 1966.Photograph by Vincent Tullo for The New York Times; painting by Camille NormanThat a love parade attends him wherever he goes — I’m part of it, having worked for him 40 years ago, sleuthing for a lost score — doesn’t mean he’s a pushover. At the sitzprobe he spoke rarely but made his points. Wanting a song called “A Simple Thing Like That” to be “less waltzy,” he suggested removing the triangle from the downbeats. For “Light,” one of the new Kander-Miranda songs, painting in ethereal music a portrait of Manhattanhenge, he asked for a more unpredictable spacing of the dissonant chords that bring it to such a startling close. And “Gold,” a flamboyant conga sequence, needed more schmaltz. “Lower your standards,” he instructed the orchestra.As that sampling of song types attests, “New York, New York” tells many stories, about people from many backgrounds. The main one is the troubled romance between a Black singer (Anna Uzele) and an Irish musician (Colton Ryan). Secondary ones concern a Polish refugee and his violin teacher; a Cuban drummer and his mother; and a Black trumpet-playing GI. Most have come to New York after World War II to make art or save their souls — or both at once. As a new song called “Major Chord” puts it, they seek the trifecta of “music, money, love.”“Maybe you get one, maybe you get two,” Stroman said. “But it’s hard to get three.”Still, Kander adds, summing up the theme, “New York is where you have the best chance of being who you see yourself as.”He would know, having come here for just that reason, in 1951, after college and military service. The banners welcoming his transport ship from the Pacific — “Welcome Home! Well Done!” — immediately made sense: This was where he was meant to be.The “well done” part he does not take as seriously; his service was mostly spent playing piano for officers and at one point running $400,000 worth of Canadian Club whisky to Manila — along with 11 cows.Yet “well done” surely applies to him now. “He lives his life correctly,” Stroman observed. Perhaps that’s why no one speaks invidiously of him, even though few major chords are as undiminished as his. Music, he has abundantly; money, in spades — “Chicago” alone, the longest-running American musical ever on Broadway, has grossed more than $1.6 billion worldwide. And love, absolutely, even if it had to wait until his 50s. “Happiness is one of the last things you learn, if you ever do,” he said.Joel Grey, center, atop a platform, as the master of ceremonies of the Kit Kat Club in the original Broadway production of “Cabaret.”PhotofestChita Rivera as the film star Aurora in “Kiss of the Spider Woman,” which debuted on Broadway in 1993.Michael Macor/The San Francisco Chronicle, via Getty ImagesCharlotte D’Amboise as Roxie Hart in the Broadway revival of “Chicago,” which has been running since 1996.THAT HE IS ADORED by younger colleagues is partly because he serves as a beacon of the possibility of lifelong growth. (Taking them to lunch when they are barely known, as he took Miranda, doesn’t hurt either.) Stroman marvels at the muscle of his musical storytelling, built up by decades of doing it. “If I say to him ‘I imagine a girl walking down the beach and she meets the love of her life,’” she said, “he can leap up to the piano and that is exactly the story you hear in his melody.”But for Kander, aging as an artist is less about the expansion than the concentration of skill. “By the time Verdi wrote ‘Falstaff,’ when he was almost 80,” he said, “he had learned to do in 16 measures what in ‘Nabucco’” — 50 years earlier — “would have taken him a big aria and a cabaletta and all that. There’s nothing wasted, no decoration, just the thing itself. I’m not lucky enough to have had that experience a lot, but I recognize it when I see it and it almost makes me laugh.”There’s that modesty again, reflexive but also pragmatic. Stroman summarizes the two biggest things she’s learned about collaboration from Kander as “no bad ideas” — which actually means plenty of them, freely offered and freely rejected — and “leave egos at the door.” Kander wants his drama onstage only.“What we do is a craft,” he insisted. “I mean you can have a great inner talent, and a lot of people do, but without craft it’s very hard for the talent to emerge. Also the reverse is true. You may not feel particularly inspired by a commitment you’ve made, or a moment you’re supposed to create, but you still have to write those 12 bars to cover someone crossing the stage.”Even worse, you might have to write a second version of “New York, New York.” When De Niro complained that the first was too “light,” Kander and Ebb, in a snit, tossed off the famous one in 45 minutes. “Which does the job and audiences like it and De Niro was right and it’s a great piece of luck,” Kander said ruefully. “But I just don’t get it.”At the sitzprobe, they got it. When the brass and saxes swung in big at the top of the tune, the cast reared back, as if hit by a tornado. Tears of something like joy flew from their eyes, if not from Kander’s. When I later forced him to name some songs he’s actually proud of, he admitted only to ballads, not Ebb’s beloved “screamers.” “I Miss the Music” from “Curtains.” “I Don’t Care Much,” written as a dinner boast between coffee and dessert. And a new one, set in the Whispering Gallery at Grand Central Station, perhaps inevitably called “Can You Hear Me?”Off the top of my head, I could name 30 others he ought to include.“I appreciate that, but it’s independent of me. My fingers find something, as if they have little brains of their own. The keyboard is my friend, since I was 4. Being an artist is much more like being a carpenter than like being God: Something will happen. Or you tear it up. And start again.”A horse can’t do any better. More