With hits such as “Love to Love You Baby,” “I Feel Love,” “Hot Stuff” and “Bad Girls,” Ms. Summer came to embody disco’s sexually liberated culture. She sold more than 20 million records and became one of the first performers to have three consecutive double-disc albums reach No. 1 on the charts.
Her forthright sexuality and throaty voice helped Ms. Summer blaze a path that Madonna, Lady Gaga and Rihanna have followed.
For her dominance of 1970s pop, Ms. Summer was dubbed the Queen of Disco. But she bristled at the moniker’s narrow scope. “It’s nice to be the queen of something,” she told the New York Times in 1996, adding, “They can call me what they want as long as they pay me.”
Trained initially in gospel singing, she had a remarkable range and accumulated five Grammy Awards for singing rock, rhythm and blues, gospel and dance music. She co-wrote many of her hip-gyrating disco tunes.
In a 1984 assessment of her career, Times pop music critic Robert Palmer wrote that Ms. Summer “made some of the freshest, most substantial dance records of a period noted for its froth and foolishness.”
Ms. Summer launched her professional career in the late 1960s by moving to Europe to sing in a production of the rock musical “Hair.” She spent eight years overseas performing in stagings of “Godspell” and “Porgy and Bess” and eventually met producers Giorgio Moroder and Pete Bellotte.
She had minor success in Europe during the early 1970s singing “The Hostage” and “Lady of the Night” before exploding to stardom with the 17-minute opus “Love to Love You Baby.” The song was a disco rendition of the 1960s Serge Gainsbourg and Jane Birkin erotic duet “Je T’Aime . . . Moi Non Plus” (“I Love You . . . Me Neither”).
With Ms. Summer’s sultry moans, breathy singing and sexually explicit lyrics — “Do it to me again and again” — the song became an instant hit in discotheques and underground clubs. (Ms. Summer, citing her upbringing in a strict and religious household, said she approached the song as a piece of theater and was merely acting her part.)
Propelled by “Love to Love You Baby,” Ms. Summer returned to the United States in 1975 as one of disco’s shining stars.
She found greater success with the 1978 album “Live and More,” which featured her singing concert versions of “MacArthur Park,” popularized by actor Richard Harris, and “Last Dance.”
Ms. Summer’s 1979 album “Bad Girls” hit No. 1 on the Billboard top 200, powered by hits including “Hot Stuff” and the catchy, horn-infused “Bad Girls.”
Ms. Summer said her 1983 hit “She Works Hard For the Money” was inspired by a trip to the restroom. She was at a Grammy Awards party when she spotted the women’s restroom attendant asleep from exhaustion.
“And my first thought was, ‘God, she works hard for her money, that lady,’ ” Ms. Summer told ABC news in 2008. She quickly returned to the restroom and began composing the song on toilet paper.
Ms. Summer’s lasting popularity was buoyed by legions of black, Latin and gay fans. Her electrifying performances were known to draw sellout crowds.
During a 1998 concert at Carnegie Hall in New York, Billboard magazine wrote that after two hours of raucous — but polite — ovations, the audience couldn’t take it anymore. After “a salacious guitar-drenched rendition of ‘Hot Stuff,’ ” Billboard wrote, “fans rushed down the red carpeted aisles toward the stage.”
LaDonna Adrian Gaines was born on Dec. 31, 1948, and grew up in Boston, where her father worked as a butcher, janitor and electrician. Her mother was a schoolteacher.
In Germany, she married Austrian actor Helmut Sommer and changed her last name to Summer. After they divorced, Ms. Summer married musician and producer Bruce Sudano. Besides Sudano, survivors include a daughter from her first marriage and two daughters from her second marriage.
Amid Ms. Summer’s success in the late 1970s, she suffered from depression and attempted suicide. She wrote in her 2003 memoir that she climbed onto the windowsill of her Central Park hotel room. As she leaned out, her foot got caught in the drapes, preventing her fall. She became a born-again Christian by the mid-1980s, and many of her later songs had religious themes.
Yet it was her more raucous early work that influenced generations of female performers. Rolling Stone magazine wrote in 2003: “Madonna’s career without Summer and ‘Bad Girls’? Unthinkable.”