At 17, the Brooklyn-born, Tenafly, New Jersey-raised former Lesley Sue Goldstein wailed in a hit single produced by Quincy Jones that "It's My Party" and she would cry if she wanted, whining of a rival, "She's a Fool," and declaiming, "You Don't Own Me."
The catchy beat and voice led to four Top 5 singles in 1963 – and a 1965 smash by a then-brand-new composer enjoying his first hit: "Sunshine, Lollipops and Rainbows," by Marvin Hamlisch.
Of her first and biggest hit, "Party," Gore recalled for a 2005 interview, "We recorded [it] on a Saturday afternoon, March 30, and I heard the record for the first time on April 6. I was driving to school, literally seven days later ... so when it started getting played, we weren't prepared for it. We didn't even know it had been released."
In fact, she said, she wasn't even sure the public would ever get to hear the effort in the first place.
"When we left the studio, everyone was pleased, but even the president of the company, a wonderful father-like figure, Irving Green, said, 'Now, sweetheart, if this never gets released, I don't want you to be disappointed.' And I said, 'It's okay, this has been a great experience. I enjoyed it and I thank you for that, and it's okay if you never release it.' I never thought it would see the light of day."
After graduating from Sarah Lawrence College, Gore saw her star stall, though fans still happily recall her January 1967 turns as Pussycat, who worked with Catwoman, on ABC's Batman series.
However, when a 1976 comeback album sank, Lesley penned lyrics for brother Michael (Fame) Gore.
By the '90s, however, nostalgia kicked in and Gore – whose signature song never went out of fashion – became a popular draw in clubs, at fairs, even in arenas.
"It's amazing," she told PEOPLE in 1992, "to see 4-year-olds lip-synching 'It's My Party.' "
Besides her brother and mother, Gore is survived by her partner of more than three decades, Lois Sasson.