She once called the song, a No. 1 hit in 1975, “catchy, corny and commercial,” but loved the way it united the Black, gay, disco and funk audiences Labelle was drawing, with its glam look and far-reaching lyrics. “It really did bring people together,” she told me, “because it’s very difficult for you to hate when you’re dancing.”

The group knew “Marmalade” — written by the songwriter-producers Bob Krewe and Kenny Nolan — was a winner during its recording, with Allen Toussaint in his New Orleans studio, LaBelle said, even though she had no idea what its now-famous chorus “Voulez-vous coucher avec moi?” meant. “We thought it was just a fun song,” LaBelle said, “then finding out it was about a hooker! But she has to make her money too. So we kept singing.”

By then, Hendryx had taken an interest in the logistics of recording, and migrated to the engineer’s side of the booth — almost unheard-of for a female artist, or any woman, in that era. Roberta Grace, an assistant engineer on that session, was a rare exception, later teaching Hendryx how to solder wires for her own board. “I wasn’t happy with the sound” on “Lady Marmalade,” Hendryx recalled, and because she and the band pushed, it was mixed again.

The trio had no more chart-toppers, though, and Hendryx, who had been their main songwriter, stepped out on her own. She never quite achieved the same level of public acclaim, even as she earned critical attention and a wider artistic circle of downtown rockers, along with a Grammy nomination in 1985, for “Rock This House,” recorded with Keith Richards.