At Joe’s Pizza on Carmine Street, Marc Shaiman, the celebrated composer and lyricist, dropped his slice on the floor. “Ugh, it’s the Shaiman vortex,” he said. “Everything I come near breaks.”

Shaiman, sixty-six and a self-described Eeyore, with a scruff of white beard, was feeling fragile. He’d spent the past week holed up in his Chelsea apartment, obsessively rerecording a Barbra Streisand anecdote for the audiobook of his new memoir, “Never Mind the Happy: Showbiz Stories from a Sore Winner.” It had been a tough year, with a barrage of losses—most recently, his golden retriever, Chops, had died suddenly at the upstate house he shares with his military-veteran husband, an event so disturbing that Shaiman has imagined tearing up the floor where it happened. During a classroom visit at N.Y.U.’s drama school, the students’ angelic harmonies, plus a request for a deep cut of his—“Drifting,” a ballad of insecurity inspired by his collaborator and ex, Scott Wittman—got Shaiman so choked up that he worried he’d scared the young artists.

But strolling over to Marie’s Crisis Café, the venerable show-tune sing-along joint, he perked up. He gazed over at the marquee of the IFC Center, formerly the Waverly Theatre, and said, “Me and Sal were hams.” On a snowy night in 1976, the teen-age Shaiman and his friend Sal Piro had impulsively joined the line for a screening of “The Rocky Horror Picture Show.” They came back the next night, then nearly every weekend for months, tossing out zingers and building a shared queer ritual from scratch. Shaiman’s contributions included a reference to an old Shake ’n Bake TV ad: “And we helped!”

“It was the best time of my life,” Shaiman said, with a grin. “You’re fearless when you’re young.” At the downtown venue Club 57, he and Wittman had staged camp productions, like “The Sound of Muzak,” starring Holly Woodlawn (“When the dog bites / When my pee stings”). Then Shaiman rocketed to success—touring with his hero Bette Midler, in the seventies, playing piano on “Saturday Night Live,” in the eighties, and scoring a panoply of movie hits, many in collaboration with Rob Reiner. Shaiman co-wrote the music and lyrics for the first “South Park” movie (a fart tap dance was his idea); in the two-thousands, he co-created a series of major musicals (“Hairspray,” “Smash”). There were pot years and coke years, good times and bum times—or, in his words, “for every plotz, a zetz.”

At the bar at Marie’s, Shaiman ran into a casting director he’d last seen at a memorial service for the conductor Glen Roven. In the late eighties, Roven had been cast with Shaiman in the film “Broadcast News,” for a famous scene in which the two of them pitch a network-news theme song. (“Big finish!”)

Cartoon by Ellis Rosen

“He and I were the same person, pretty much,” Shaiman said, sipping a Diet Coke—two short, gay Jewish boys, teen tyros chasing the ultimate high: perfect composition. The casting director told Shaiman that Roven had been “in awe” of his talent.

“We were insanely jealous of each other!” Shaiman said, with a laugh.

When the bar crowd launched into the score of “Les Misérables,” Shaiman announced, “That’s when the bitterness began!” He’d rankled at the rise of the British “spectacle” musical, back in the eighties. He still recalls every bump in the road, enumerating old Twitter wars, critics who’d called his songs “unmemorable,” and short-lived labors of love like the musical adaptation of “Catch Me If You Can,” which haunt him, even now. He’s had Broadway blockbusters and seven Oscar nominations; he’s thrilled that his trans-positive musical adaptation of “Some Like It Hot” has been embraced on tour, even in red states. But taking risks doesn’t get easier. “My skin has gotten thinner instead of thicker,” he said.

During a break, the house pianist invited Shaiman to the keyboard, where he unspooled his origin story for the crowd: he’d wandered into Marie’s at sixteen, and, in a Hollywood miracle, the owner clocked his piano skills and tipped him off to a job at the Duplex, down the street, plus a gig playing piano at Marie’s. (Shaiman had lied about his age.) He quit Marie’s a few months later, shortly after a New Year’s party where the staff hung him off the balcony in a diaper. By then, he was staying in Wittman’s place on Seventy-ninth Street, conveniently situated across the hall from one of Midler’s backup singers, known collectively as the Harlettes.

Shaiman stood up to hammer out a rollicking version of “Good Morning Baltimore,” then collapsed back onto the piano bench. “I’m exhausted,” he joked, and asked if there were any requests.

“ ‘They Just Keep Moving the Line’?” a sweet-faced brunette called out.

He looked worried. “Do you know that one?” he asked the crowd.

Not everyone did, but people read the lyrics off of their phones. In a wobbly voice, the brunette began the number, from “Smash,” getting bolder by the climax. “So I made friends with rejection / I’ve straightened up my spine!” Then the crowd chimed in, belting out Shaiman’s perfect ode to never feeling like you’ve nailed it. ♦