San Francisco — San Francisco Mayor Daniel Lurie had declared it Michael Tilson Thomas Day. City Hall glowed MTT’s trademark blue. Davies Symphony Hall, where Tilson Thomas presided over the San Francisco Symphony for an influential quarter century, was festooned with giant blue balloons.

For Tilson Thomas, it all was the culmination of what he declared in February: “We all get to say the old show business expression, ‘It’s a wrap.’”

Despite starting treatment for an aggressive form of brain cancer in summer 2021, Tilson Thomas astonishingly continued to conduct throughout the U.S. and even in Europe for the next three and a half years. But in February he learned that the tumor had returned, and the conductor declared last Saturday night’s San Francisco Symphony gala, billed as an 80th tribute to this native Angeleno, would be his last public appearance.

He was led to the podium by his husband, Joshua Robison, who remained seated on stage, keeping a watchful eye. Tilson Thomas started with Benjamin Britten’s Variations and Fugue on a Theme by Purcell, better known as “The Young Person’s Guide to the Orchestra.” After various tributes and performances in his honor, MTT, ever the great showman, went out with a bang, leading a triumphant and mystical and stunningly glorious performance of Respighi’s splashy “Roman Festivals.”

A song from Leonard Bernstein’s “On the Town” — including the line “Where has the time all gone to?” — followed as an encore, sung by guest singers and the San Francisco Symphony Chorus, just before balloons joyfully fell from above.

For six decades, beginning with his undergraduate years at USC — where he attracted the attention of Igor Stravinsky, Aaron Copland, Jascha Heifetz, Gregor Piatigorsky and the odd rock ‘n’ roll musician about town — Tilson Thomas has been a joy-making key figure in American music.

To pin MTT down is an unreasonable task. He saw a bigger picture than any great American conductor before him — his mentor and champion, Bernstein, included. With a pioneering sense of eclecticism, he connected the dots between John Cage and James Brown, between Mahler and MTT’s famous grandfather, Boris Thomashefsky, a star of the New York Yiddish theater.

Tilson Thomas has nurtured generations of young musicians and given voice to outsiders greatly responsible for American music becoming what it is. He treated mavericks as icons — Meredith Monk and Lou Harrison among them.

The San Francisco concert could touch on little of this, but it did reveal something of what makes MTT tick. In “Young Person’s Guide,” for instance, Tilson Thomas demonstrated an undying love of every aspect of the orchestra as well as his lifelong devotion to education. As a 25-year-old Boston Symphony assistant conductor, he was speaking to audiences, sharing enthusiasm that not all uptight Bostonians were quite ready for.

Not long after, he succeeded Bernstein in the New York Philharmonic Young People’s Concerts. He made television and radio documentaries. In 1987, he founded the New World Symphony in Miami Beach, training orchestra musicians. Alumni are now busy reinventing American orchestral life. In L.A., former New World violinist Shalini Vijayan curates the imaginative Koreatown new music series Tuesdays @ Monk Space.

With the young conductor Teddy Abrams at his side turning pages, Tilson Thomas treated “Young Person’s Guide” more as a seasoned player’s guide to the orchestra. A hallmark of Tilson Thomas’ tenure in San Francisco had been to encourage a degree of free expression typically stifled in ensemble playing. Britten’s score is a riot of solos, and this time around they all seemed to be saying, in so many notes: “This is for you Michael.”

This is for you, Michael, as was all else that followed. While Tilson Thomas sat in a chair at the front of the stage looking at the orchestra, Abrams — music director of the Louisville Orchestra and a Berkeley native who began studying at age 9 with Tilson Thomas — led the rousing overture to Joseph Rumshinsky’s Yiddish theater comedy, “Khantshe in Amerike.” Bessie Thomashefsky, Tilson Thomas’ grandmother, was the original Khantshe in 1915.

Throughout his career Tilson Thomas has been an active composer, but only in recent years had he finally began more actively releasing his pensive and wistful songs that served as informal entrees in a private journal. Mezzo soprano Sasha Cooke led off with “Immer Wieder” to a poem by Rilke. Frederica von Stade, still vibrant-sounding at 79, joined her for “Not Everyone Thinks I’m Beautiful.”

The two songs tenor Ben Jones turned to, “Drift Off to Sleep” and “Answered Prayers,” were moving odes to melancholy. The Broadway singer Jessica Vosk — whose career in show business was launched when Tilson Thomas picked her out of the San Francisco Symphony Chorus to be a soloist in “West Side Story” — lifted spirits with “Take Back Your Mink” from “Guys and Dolls,” but then reminded us why we were all there with Tilson Thomas’ “Sentimental Again.”

Cooke sang “Grace,” which Tilson Thomas wrote for Bernstein’s 70th birthday but which here took on a brave new meaning in its final stanza: “Make us grateful whatever comes next / In this life on earth we’re sharing / For the truth is / Life is good.”

Edwin Outwater, who got his start as an assistant conductor to Tilson Thomas in San Francisco, led the inspirational finale of Bernstein’s “Chichester Psalms” before Tilson Thomas returned to raise the roof with “Roman Festivals.”

Respighi’s evocations of gladiators at the Circus Maximus, of early Christian pilgrims and other scenes of ancient Roman life, seem a surprisingly odd epilogue to an all-American conductor’s storied career. But Tilson Thomas has always been an arresting programmer, even in his 20s when he served as music director of the Ojai festival. “Roman Festivals” has long been a Tilson Thomas favorite. He recorded it with the L.A. Phil in 1978, relishing the details of ancient Rome in all its intricate and realistic complexity.

This last time, Tilson Thomas offered an epic, yet longing, look back. Trumpets blared with startlingly loud majesty. Pilgrims were lost in stunning meditative refinement. In the last of the four festivals, “The Epiphany,” grace and grandeur merged as one, with final, firm orchestral punctuation massively powerful. It was as if Tilson Thomas was saying to the audience, “This one is for you. And I’m still here saying it.”

Tilson Thomas has made a practice of musing about what happens when the music stops. What is left? How long does the music stay with us, somewhere inside? Can it change us? Does it matter?

From the instant Tilson Thomas became music director of the San Francisco Symphony in 1995, he treated the orchestra as an essential component of San Francisco life. His successor, Esa-Pekka Salonen, has taken that to heart with the kind of innovatory spirit that he had brought to the L.A. Phil. The orchestra’s management has not, however, provided needed support, and Salonen is leaving in June. Musicians stood outside Davies handing out fliers to the audience demanding that the orchestra pursue Tilson Thomas’ mission.

The San Francisco Symphony has reached a turning point. Respighi wrote of “The Epiphany” that he wanted frantic clamor and intoxicating noise, expressing the popular feeling “We are Romans, let us pass!” Tilson Thomas beat out those three emphatic staccato orchestral chords — Let! Us! Pass! — as though meant to ring and ring and ring, as lasting as centuries-old Roman monuments.