For much of her more than 40 years at RCA, Ms. Gabriel was a producer, overseeing “Living Strings” and other profitable lines.Ethel Gabriel, who in more than 40 years at RCA Victor is thought to have produced thousands of records, many at a time when almost no women were doing that work at major labels, died on March 23 in Rochester, N.Y. She was 99.Her nephew, Ed Mauro, her closest living relative, confirmed her death.Ms. Gabriel began working at RCA’s plant in Camden, N.J., in 1940 while a student at Temple University in Philadelphia. One of her early jobs was as a record tester — she would pull one in every 500 records and listen to it for manufacturing imperfections.“If it was a hit,” she told The Pocono Record of Pennsylvania in 2007, “I got to know every note because I had to play it over and over and over.”She also had a music background — she played trombone and had her own dance band in the 1930s and early ’40s — and her skill set earned her more and more responsibility, as well as the occasional role in shaping music history. She said she was on hand at the 1955 meeting in which the RCA executive Stephen Sholes signed Elvis Presley, who had been with Sun Records. She had a hand in “Cherry Pink and Apple Blossom White,” the 1955 instrumental hit by Pérez Prado that helped ignite a mambo craze in the United States.She may have produced or co-produced the album that contained that tune, but April Tucker, lead researcher on a documentary being made about Ms. Gabriel, said details on the early part of her career were hazy. Ms. Gabriel often said that she had produced some 2,500 records. Ms. Tucker said officials at Sony, which now holds RCA’s archives, had told her that the number may actually be higher, since contributions were not always credited.In any case, by the late 1950s Ms. Gabriel was in charge of RCA Camden Records, the company’s budget line, and was earning producer credits, something she continued to do into the 1980s.In 1959 she began the “Living Strings” series of easy-listening albums, consisting of orchestral renditions of popular and classical tunes (“Living Strings Play Music of the Sea,” “Living Strings Play Music for Romance” and many more), most of which were released on Camden. The line soon branched out into “Living Voices,” “Living Guitars” and other subsets and became a big profit-generator for RCA — which was not, Ms. Gabriel said, what the boss expected when he put her in charge of Camden, a struggling label at the time.“I’m sure he thought it was a way to get rid of me,” she told The Express-Times of Easton, Pa., in 1992 (too diplomatic to name the boss). “Well, I made a multimillion-dollar line out of it, conceived, programmed and produced the entire thing.”Ms. Gabriel with her fellow producers Don Wardell, left, and Alan Dell at the 1983 Grammy Awards. They shared the award for best historical album for “The Tommy Dorsey-Frank Sinatra Sessions.” Ed and Nancy MauroThere were other profitable series as well. Ms. Gabriel was particularly good at repackaging material from the RCA archives into albums that sold anew, as she did in the “Pure Gold” series. In 1983 she shared a Grammy Award for best historical album for “The Tommy Dorsey-Frank Sinatra Sessions” By the time she left RCA in 1984, she was a vice president.Yet, unlike the top male record executives of the era, she rarely made headlines. Ms. Tucker, an audio engineer, said she had never heard of Ms. Gabriel until one day she went searching to see if she could find out who the first female audio engineer was. She brought Ms. Gabriel to the attention of Sound Girls, an organization that promotes women in the audio field, and soon Caroline Losneck and Christoph Gelfand, documentary filmmakers, were at work on “Living Sound,” a film about her.Ms. Losneck, in a phone interview, said they had been hoping to complete the documentary by Ms. Gabriel’s 100th birthday this November.Ms. Losneck said Ms. Gabriel had survived in a tough business through productivity and competence.“She knew who to call when she needed an organist,” she said. “She knew how to manage the budget. All that gave her a measure of control.”Many of the records Ms. Gabriel made fit into a category often marginalized as elevator music.“It’s easy to look back on that music now and say it was kind of cheesy,” Ms. Losneck said, “but back then it was part of the cultural landscape.”Toward the end of her career, as more women began entering the field, Ms. Gabriel was both an example and a mentor. Nancy Jeffries, who went to work in RCA’s artists-and-repertoire department in 1974 and had earlier sung with the band the Insect Trust, was one of those who learned from her.“Being a woman and having ambition at a record company in those days was something that just didn’t compute with most of the male executive staff, but I was fortunate enough to land in the A&R department at RCA Records, where Ethel was established as a force to be reckoned with,” Ms. Jeffries, who went on to executive positions at RCA, Elektra and other record companies, said by email. “She had developed a couple of deals that, while they weren’t particularly ‘hip,’ generated a lot of income and financed some of the more speculative workings of the department. Lesson one: Make money for the company and they will leave you be.”Mr. Mauro summarized his aunt’s career simply:“She was successful early on when the playing field wasn’t level.”Ms. Gabriel, interviewed by The Cincinnati Enquirer in 1983, had a succinct explanation of her ability to thrive in a man’s world.“I didn’t know I was somewhere I shouldn’t be,” she said.Ethel Nagy was born on Nov. 16, 1921, in Milmont Park, Pa., near Philadelphia. Her father, Charles, who died when she was a teenager, was a machinist, and her mother, Margaret (Horvath) Nagy, took up ceramic sculpture later in life.Ms. Gabriel studied trombone in her youth and formed a band, En (her initials) and Her Royal Men, that played in the Philadelphia area. While at Temple she began working at RCA in nearby Camden putting labels on records and packed them before advancing to record tester.Ms. Gabriel at her home in Rochester, N.Y., in 2019. She had a succinct explanation of her ability to thrive in a man’s world: “I didn’t know I was somewhere I shouldn’t be.”Living Sound FilmAfter graduating in 1943, Ms. Gabriel continued her studies at Columbia University and worked at RCA’s offices in New York, including as secretary to Herman Diaz Jr., who led RCA’s Latin division. She spent a lot of time listening in on studio sessions, and by the mid-1950s trade publications were referring to her as an “RCA Victor executive.”In 1958 she married Gus Gabriel, who was in music publishing. The couple counted Frank Sinatra as a friend. In a 2011 interview with The Rochester Democrat and Chronicle, she said that in 1973, when her husband was dying in a hospital, she walked into his room one day and found his nurses in a tizzy.“I asked, ‘What’s wrong?’” she recalled. “They said, ‘Oh, everybody got autographed pictures from Sinatra!’”Ms. Jeffries said that Ms. Gabriel had always mentored the women at the company no matter where they were on the corporate ladder. But her helping hand was extended to men, too, as the producer Warren Schatz found out when he joined RCA in the mid-1970s, as the disco wave was building.He had an idea for an album that might catch that wave, he said, and she came up with $6,000 to get it made. It was by the Brothers and included a song, “Are You Ready for This,” that became a dance-floor staple.“So Ethel basically started my life off at RCA,” Mr. Schatz said in a phone interview. Soon he was vice president of A&R, and she was reporting to him.“Whatever she wanted to do, I would just say yes to,” he said. “She was so calm, and so knowledgeable, and so self-sufficient.”Ms. Gabriel left RCA in 1984, in part, she said, at the urging of Robert B. Anderson, a former U.S. treasury secretary, who persuaded her to turn over to him her retirement package — more than $250,000 — so that he could invest it in the hope that the proceeds would finance future music ventures. The money disappeared, and Mr. Anderson, who died in 1989, was later convicted of tax evasion.Ms. Gabriel lived in the Poconos for a number of years before moving to a care center in Rochester to be near Mr. Mauro and his family. As she died at a hospital there, Mr. Mauro said, the staff had Sinatra songs playing in her room. More