Mr. Moroder isn’t cocky about what he has accomplished or the comeback he’s enjoying. In person, he comes across less like the mac daddy of disco, and more like its avuncular Mr. Magoo.
He went to Studio 54 just once during its heyday and recalls spending much of the evening fretting that “I Feel Love” hadn’t sounded on its speakers the way he’d wanted it to. “It was the way I split up the bass between the left and the right side,” Mr. Moroder said. “It was a small thing which bothered me.”
Other than high-calorie food, his main vice is the occasional shot of vodka, which he takes after his D.J. sets are over. His clothes (black Hugo Boss shirt, black pants from who knows where and Prada shoes) are nondescript. The most louche thing about him is his mustache.
Also, there are no groupies in his dressing room, though they do try to get in, according to his wife, Francisca, who this evening stood guard by the door in a white dress.
When Mr. Moroder teamed up with Ms. Summer in 1974, he was a Munich-based composer from the province of South Tyrol in Italy, whose previous hits had a Beach Boys-by-way-of-Saint-Tropez feel. Ms. Summer was a singer in the traveling European cast of “Hair,” trying “to survive,” he said.
Their 1974 pop album had a couple of minor hits in Europe but failed to land her an American record deal. Then, as groups such as the Love Unlimited Orchestra and the Hues Corporation popularized the disco sound, Ms. Summer recorded “Love to Love You Baby,” an erotic cornucopia that featured her mimicking an orgasm as she pleaded to a lover, “Do it to me again and again.”
The way Mr. Moroder recalled it, he and Ms. Summer figured the song was an experiment that would go nowhere. “We both thought it would be a little too much,” he said.
Instead, as it went to No. 2 on the Billboard Hot 100 and spent four weeks atop the dance charts, Casablanca Records signed her and sent Mr. Moroder back to the studio to record a 17-minute D.J. version.
Two years later, Mr. Moroder brought out a Moog synthesizer for “I Feel Love,” which had a hard, space-age bent, and became an era-defining track.
Brian Eno heard “I Feel Love” while in the studio with David Bowie and proclaimed it to be “the sound of the future.” Debbie Harry and her Blondie compatriots did a punk version of it at CBGB. In 2006, Madonna sang it while on tour for her Moroder-influenced album, “Confessions on a Dance Floor.”
Few in attendance at Schimanski looked as if they’d been alive the first time it came out, but most knew who Mr. Moroder was. “He’s one of my idols,” said Whitney Tai, a young singer/songwriter who had on gold lamé pants and a white top that said “K Bye.”
When Mr. Moroder took over the D.J. stand at around 11 p.m., a crowd of more than 500 raised camera phones as he plunged into a brisk hourlong set of his greatest hits that started with “Love to Love You Baby” and included at least five other songs he had worked on with Ms. Summer.
Mr. Moroder also played two of his Academy Award-winning songs from the ’80s, “Flashdance … What a Feeling” (sung by Irene Cara for the movie “Flashdance”) and “Take My Breath Away” (sung by Berlin for “Top Gun”).
Mr. Moroder didn’t pretend at the mixing board to be the next Avicii or Frankie Knuckles as he used a beat-matching program on his laptop to segue between songs, which also included his 2014 single, “74 Is the New 24” and a cover of the Suzanne Vega’s “Tom’s Diner” featuring Britney Spears.
Nor did Mr. Moroder proclaim to have forged a close bond through this late collaboration. Ms. Spears, he said, simply sent him her vocal track and he laid it down over an electro-ish beat.
His relationship with Ms. Summer was much closer, particularly toward the end of her life. “I saw more of her those last two years than I had in the 20 before,” said Mr. Moroder, who lives in Los Angeles with Francisca and frequently had dinner with Ms. Summer there in a high-rise building on Wilshire Boulevard where they both had apartments.
Ms. Summer didn’t tell Mr. Moroder how sick she was. But she left clues. “She kept talking about these juices she was drinking and that I should be, too,” he said.
A month before her death, she sent him an emotional letter thanking him for the role he’d played in her life. “I thought, ‘Whoa,’” he said. “It was eerie.”
No wonder he seemed a little emotional as he took over the mike at the end of his set. After thanking the crowd for being “a wonderful audience,” he introduced the song whose birthday they were celebrating. Perhaps, he said, this could become a tradition.
“Come back in 10 years and we’ll celebrate again,” he said. “‘I Feel Love’ at 50!”