It was the reopening night of “The Phantom of the Opera” on Broadway, and Andrew Lloyd Webber was D.J.-ing the after-party.

From a booth built earlier that day on 44th street in Manhattan, Mr. Lloyd Webber, the play’s composer, whose career has lasted decades and who has won four Tonys and an Oscar, mixed music, clapped on all four beats, waved his hands in the air, and bobbed his head before a crowd gathered outside. (He was sporting paprika-hued Beats by Dre headphones for the occasion.)

The party followed the first performance of “Phantom” since the pandemic began, which was attended by Laura Linney, Joel Gray, several contestants of “The Bachelorette,” some “Real Housewives of New York” and Senator Chuck Schumer.

Outside the theater after the show, throngs of “Phantom of the Opera” devotees — known as “phans” — hoisted their phones to capture the 73-year-old composer playing D.J. as costumed cast members danced and lip synced on the Majestic Theater’s balcony behind him.

Mr. Lloyd Webber followed the “Phantom” theme with the Baha Men’s “Who Let the Dogs Out,” perhaps an oblique reference to Mojito, his new black Havanese. The dog, sadly, had to stay home in England with Mr. Lloyd Webber’s two Turkish Van cats.

“Mojito had his hair cut today,” Mr. Lloyd Webber said at a pre-party at Barbetta, an Italian restaurant on 46th Street. “He’s not very happy.”

Mr. Lloyd Webber, on the other hand, was effusive about what he jokingly called his “new career” as a D.J., saying that the night’s set was just a warm-up before his “big gig in Ibiza.”

The spectacle of Andrew Lloyd Webber as D.J. was novel to the point of unbelievable, but his daughter Bella Lloyd Webber, who manages his social media accounts, insisted he was doing more than just hitting play.

“He’s mixing,” she told me as she edited a video for the composer’s TikTok account on her phone behind the D.J. booth. “Lightly mixing, but mixing.”

As he played a set that included a remix of “Itsy Bitsy Teenie Weenie Yellow Polka Dot Bikini,” the crowd mostly gawked and recorded videos.

“I bet no other Broadway composer has done this!” shouted Madeleine Lloyd Webber, Mr. Webber’s wife, as she danced in the street. “You’re watching D.J. Webz,” she added, helpfully spelling out her husband’s nom de guerre as Lady Gaga’s “Rain On Me” blared. “We definitely want her to do one of our shows one day,” she said.

On the other side of the platform, Leah McSweeney of “The Real Housewives of New York City” popped bubble gum and bopped along to the music in a short leopard print dress.

Ms. McSweeney, who was accompanied by her mother, Bunny, said at intermission that the show was making her want to date again. “It’s very sexy,” she said. “The Phantom’s hot.”

A fellow castmate on “The Real Housewives,” Luann de Lesseps, was also at the show.

Inspired by the production’s set design, she said, “I wish I had that many curtains,” as she left the show.

The crowd outside the theater resembled a goth-themed prom, with phans decked out in velvet gowns, burgundy-and-black tuxedos and full-on Phantom cosplay.

“The Phantom of the Opera,” which was adapted from a 1910 novel by Gaston Leroux, remains the biggest musical by at least a couple of measures: longest-running on Broadway, largest orchestra currently on Broadway.

The musical features a love triangle among Christine, an opera ingénue, her suitor Raoul and the Phantom, her mysterious svengali and sometimes-captor. While the story is simple — think Persephone meets 42nd Street — the music and costuming are decidedly maximalist.

Phans seeking to emulate the romantic ruffles, lace and capes from the show have spurred a cottage industry of fabric designers and fabricators creating garments that mimic specific costumes from the show.

Kara Ritchie, who attended the after-party, boasted that her dress, created by Wenda Lynne Designs, was a facsimile of the gown worn by Christine during the song “The Point of No Return.”

Another attendee, Christina DiCillo, who wore a blue dress constructed by Prima Donna Designer, was seeing the show for the 38th time. She came with her twin sister, Francesca DiCillo — also in costume — who has seen the show only 24 times.

Some audience members had traveled hundreds of miles for the reopening. Emma Rose Lewis, the recently crowned Miss Clayland 2022, had driven alone from Ohio. She stood near the theater’s entrance, beaming in her sash and tiara, cloaked in a denim coat fringed in rhinestones.

Trevor Fezza, who wore the Phantom’s signature mask and black cape, said that he identified with the title character. “He’s misunderstood, but he has a side that you love,” he said.

Lin-Manuel Miranda, the patron saint of earnestness and enthusiasm, also showed up to the pre-party wearing his own plastic phantom mask. Asked which character he most identified with in the show, he said: “These days, I guess the owners of the opera house.”

At the pre-party, Mr. Lloyd Webber’s daughter Imogen wore a Phantom mask decorated with rhinestones. She said that she had procured the mask from Etsy, adding, “Don’t tell Cameron,” gesturing to Cameron Mackintosh, the show’s producer, who was chatting nearby with Curtis Sliwa, who is running for mayor.

Mr. Lloyd Webber’s set lasted about 30 minutes, but he managed to squeeze in two different remixes of the “Phantom” theme. Then, like the Phantom himself, he seemingly vanished from the party.

Mike Borowski, a press agent for the show who is also a D.J. on Fire Island, took over, closing his set around 11:30 p.m. with Donna Summer’s “Last Dance.”

By midnight, traffic had returned to 44th Street and things were seemingly back to normal on the block outside the theater. For those who viewed the return of “The Phantom of the Opera” to Broadway as a symbol of New York’s recovery, back to normal actually seemed pretty special.