MIAMI — Michael Tilson Thomas is 74 years old. In conductor years, that’s young.

He wears his elder-statesman mantle lightly, even with a kind of incredulity. He’s “MTT,” music director of the San Francisco Symphony, co-founder of the New World Symphony in Florida, sometime-leader of dozens of major orchestras around the world, expert communicator, breaker-down of musical genres and still, at bottom, the youngest-ever conductor of the Boston Symphony Orchestra, of whom Leonard Bernstein once said, “He reminds me of me at that age.” Thomas has been famous for so long, and boyish for so long, that he hasn’t had to struggle to attain the one or ever entirely abandon the other.

On a sunny afternoon in October, Thomas, newly recovered from heart surgery, is at his home in Miami, serving lunch. Conductors live in many places, and Thomas’s base is California, where he and his husband, Joshua Robison, grew up. But the Miami home — purchased thanks to a tip from director Hal Prince — is needed because of Thomas’s work with the New World Symphony, the orchestra he co-founded in 1987. Yachts glide past the window, behind the tiled pool; inside, the art collection includes paintings by the conductor’s father, a sometime screenwriter who played the piano for hours a day. The house is both comfortable and representative, not too personal to be a space for entertaining donors and luminaries; after all, a conductor’s life is partly public.

But upstairs, on a terrace, a spiral staircase leads to a small rectangle of a studio perched uneasily atop the house, like a fortification. There’s no decor, just a desk at one end and a keyboard and monitor at the other. Thomas calls up a musical score on his computer. It’s a song he wrote for the late jazz singer Sarah Vaughan, though she never sang it. Another comes from a group of settings of poems by Rilke, which will have their premiere at the San Francisco Symphony in January, as part of Thomas’s last season as the orchestra’s music director. In this room, rather than leading music composed by others, Thomas is creating and revising his own.

“I’ve given them 25 years,” he says of the San Francisco Symphony. “Now it’s my turn.”

MTT, this year one of the artists receiving Kennedy Center Honors for lifetime achievement, is reinventing himself yet again.

Authority, even as a student

For much of Thomas’s life, he has been depicted as the bad boy of classical music. Even now, no one’s denying the “boy” part. He has always had an air of aggressive precociousness; even as a student, he spoke with the authority, or arrogance, of the smartest person in the room. As a teenager, he accompanied and conducted the orchestra for master classes by the legendary cellist Gregor Piatigorsky and violinist Jascha Heifetz, and Piatigorsky asked him to learn Rachmaninoff’s cello sonata.

No, thank you, Thomas replied — he was specializing in Bach, Schoenberg, Boulez and Stockhausen.

“[Piatigorsky] took a couple of puffs on his cigarette,” Thomas recalls, “and said, ‘You are too talented to be a specialist. Next week, Rachmaninoff sonata.’ ”

Thomas developed his self-assurance during his childhood in Los Angeles, surrounded by his parents’ circle of artistic and intellectual friends — people who worked in Hollywood, played chamber music together and knew a cross-section of creative stars, from Stravinsky to Orson Welles. His grandparents, Boris and Bessie Thomashefsky, were major stars of the Yiddish theater in the early 20th century; Boris died before Thomas was born, but Bessie lived nearby and often visited when he was young.

“I see you. I see who you are,” he recalls her telling him. “You’re like me, you’re gonna have to really do something and become what you want to become. Whatever it takes, whatever it costs.”

Once the wunderkind started to become what he wanted, there weren’t always people like Piatigorsky around to keep him in his place, though there were plenty of mentors: Thomas studied with Ingolf Dahl at the University of Southern California; helped prepare performances for Igor Stravinsky; and went to Bayreuth to work with Friedelind Wagner, the composer’s granddaughter (though he still complains about the length of Wagner’s operas). He met Leonard Bernstein at Tanglewood and won the Koussevitzky Prize.

At 24, Thomas was with the Boston Symphony when William Steinberg took ill during a concert, and he stepped in and conducted the second half. “Mr. Thomas knows his business, and we shall be hearing from him again,” wrote the New York Times’s Harold C. Schonberg of that 1969 concert. (Sometimes critics get it right.)

After that, Thomas was seen as marked for a great future, the subject of lengthy newspaper features and speculation about a second Bernstein. But Thomas never pandered to conventional taste. His first recording with the Boston Symphony focused on music by Carl Ruggles and Charles Ives — still something of a stretch for conservative audiences — and he caused a near-riot at Carnegie Hall in 1973 by leading Steve Reich’s “Four Organs” on a BSO program.

“At the beginning,” Thomas says, “one thing that contributed to my being asked to turn up was that I knew a lot of pieces that nobody knew. So I could do the Berio ‘Epifanie’ or Stockhausen or Elliott Carter or whatever, and that’s what orchestras wanted me to come do. And then, okay, I’m also going to conduct something more in the standard repertoire” — in which, he acknowledges, he was often still finding his way.

After so much acclaim and attention, backlash was inevitable. Although some hailed his brilliance, others found him arrogant and unlikable, or criticized his technique. Instead of the starry posts foreseen for him, Thomas became music director at the midsize Buffalo Philharmonic. Then, in 1978, he was busted at John F. Kennedy Airport for drug possession, for small amounts of cocaine, marijuana and amphetamines. He resigned from Buffalo later that season, and the drug story made it all the harder to get another permanent post.

Being openly, if quietly, gay may not have helped, either. Thomas and Robison have been together since 1976. In 1985, Robison says, Thomas was already under consideration for the San Francisco Symphony music directorship, but “we already could sense that they were not ready for the both of us.”

Still, Thomas was too well established to go away entirely, and he gradually worked his way back. In the 1980s, he became principal guest conductor of the Los Angeles Philharmonic and then principal conductor of the London Symphony Orchestra, which he helped transform into the international powerhouse it is today.

In 1987, Thomas co-founded the New World Symphony, a unique training orchestra for young professional musicians and a laboratory for different ways of disseminating music, including long-distance online classes and live broadcasts on the wall outside the concert hall.

Finally, in 1995, San Francisco was ready for him. Among the highlights of his tenure have been a well-received cycle of Mahler symphonies; a wildly ambitious video, audio and Internet project called Keeping Score, offering in-depth looks at composers and works; and programs including an American Mavericks series that presented the full range of American music, from Lou Harrison to the Grateful Dead.

“His ability to create concert programs and festivals that capture the imagination of the public is extraordinary,” says Catherine Payne, a piccolo player with the San Francisco Symphony who was Thomas’s first hire in 1995. “I haven’t worked with anybody who’s such a master at programming, year after year.”

“As I’m very fond of saying, [there are] two moments of an artist’s life,” Thomas says. “Inventing yourself, it takes a lot of courage to do that. But then going the distance, which is much more challenging. To be able to sustain it physically and emotionally.”

A gem in Miami Beach

In the heart of Miami Beach, the New World Center refracts and reflects the city’s white Art Deco facades in a collection of curving surfaces and tilting blocks encased in a box of glass. Designed by Frank Gehry and opened in 2011, the building is devoted to presenting music in every way possible: Odd nooks in the public spaces can become venues for chamber concerts; speakers that snake through the park outdoors like something out of Dr. Seuss enable you to watch the live wallcasts surrounded by sound, oblivious to passing traffic. At the heart of the building is a small, blue, bowllike concert hall, alive with sound.

On a recent October day, Chad Goodman, the orchestra’s current conducting fellow, was rehearsing the orchestra in Schumann’s overture to “The Bride of Messina” while MTT sat at a keyboard and kibitzed.

“And the main problem with this is . . . ?” Thomas quizzed Goodman at the end of one passage, looking over his glasses. Goodman stumbled for the right answer: “Balance-wise, it’s . . . ”

But Thomas was already exuberantly cutting him off: “It’s too f---ing loud.”

Later, Goodman waxed enthusiastic about getting direct feedback from a major conductor. “This kind of opportunity,” he said, “doesn’t exist anywhere else.”

The New World Symphony is one of the orchestra world’s success stories. It was born as a result of Thomas’s realization, at Tanglewood, of just how uncertain life was for young musicians. There must be a more productive way for them to spend their time, he thought, than working at Domino’s to pay for lessons between auditions. Eventually, he was introduced to the Miami-based owner of a cruise ship line, Ted Arison, and the dream became a reality. The New World Symphony is an educational institution, where musicians come for three-year fellowships, honing their skills as musicians, teachers and communicators while taking auditions for orchestra jobs. Fellowships are often cut short if a musician lands a permanent position before the three-year term is over.

The organization is a concrete expression of some of Thomas’s central interests. Working with young musicians sustains him, he says. And disseminating music through technology — videos or audio, the YouTube symphony or the Internet — has been a theme of his career. The New World Center, with its state-of-the-art technology, makes both of these things possible on a grand scale, archiving every performance and master class in the building, newly equipped to record and broadcast everything in 4K HD.

“Doing it here as opposed to doing it in New York has turned out to be an enormous advantage in many ways,” Thomas says. “In New York, it would be one of many different activities and gigs that the fellows would do. Here, it’s much more focused that they’re here to learn and accomplish, and they’re getting a lot of very individual coaching inspiration. [If] you go to a major music school, you get very intensely the perspective of that school and the teacher you’re working with. When you come here, within a couple of weeks, you might be working with people from the Russian tradition, the French tradition, the Cleveland tradition, the San Francisco tradition, the Viennese tradition.”

The organization has also become a showpiece of Miami’s cultural scene. Rehearsal is briefly interrupted by a visit from Donna Shalala, the U.S. representative of Florida’s 27th Congressional District, where the New World Symphony is based, though she’s better known as the secretary of health and human services in the Clinton administration. She praises the fellows and the power of music, and calls Thomas “a treasure of Florida, and of the world.”

Yet Thomas seems to downplay his achievements. “My forte is prototypes,” he says. “Sustaining something and keeping it going is a different skill.” He says this regardless of the fact that he has been leading this organization, which he essentially invented, for 35 years.

Life and love

Joshua Robison and Michael Tilson Thomas met in an orchestra in California — Robison on cello, Thomas on oboe. They were 11 and 12. They didn’t become a couple for another two decades, during which time Robison left music (his sister is the flutist Paula Robison) and won a national college title in gymnastics. They got together in 1976, married in 2014 and share a career as they share their lives — matter-of-factly and on a granular level.

Robison is in no small part responsible for helping to sustain and keep going — even to realize — the projects that Thomas launches. Robison is sometimes described as MTT’s manager, but if anything, his role is even more central and ubiquitous. Although Robison doesn’t have an official title at the New World Symphony or the San Francisco Symphony, he has taken an active role at both, planning functions and events, overseeing things like housing for fellows, figuring out how to implement ideas — such as the LGBTQ benefit gala with Audra McDonald that the orchestra organized on short notice in 2017 after canceling performances in North Carolina in response to the state’s anti-LGBTQ laws.

“I honestly don’t think it will make all that big a difference that I’m not there as much,” Thomas told the San Francisco Chronicle of his impending retirement from the orchestra; he will be back, after all, as conductor laureate. “I think, although not as many people realize it yet, it’s going to make an enormous difference that Josh is not there.”

Indeed, for all of Thomas’s extroverted public persona, one of his driving traits is an underlying loyalty, even consideration for others. Perhaps that is what’s at the bottom of his desire to communicate about music: a boyish eagerness to make contact, to share, to play.

“When he gives a soloist a cue,” Payne says, “he does it in a way that’s unusual. He looks at you like, ‘This is going to be the most beautiful thing ever. Show me what you can do, this welcoming, inviting way.’ I’ve worked with conductors who look at you with a stern expression as they bring you in. It’s sort of a challenge. With Michael, it’s an invitation.”

Or perhaps it’s just that Thomas can’t mask his sense of delight.

“The message of all this,” Thomas says, “is that we’re all defined as ourselves in some specific way. Maybe we’re even defending our identities. But in between us is this actual play space. And if people can get their minds and their spirits out into this play space, there’s just such amazing, adventurous and rewarding things that can happen. And that is what the arts teach you to do.

“It is possible,” he continues, “through the work of various artists to learn a lot of things about how to enter this play space. And it’s possible through the arts to experience things that you might be too scared to try out in your own life. This, from the beginning, has been what I cared about. I’ve been really lucky that I’ve been able to hold onto it.”

Read more about the 2019 Kennedy Center Honorees: