Sue Mingus, who founded jazz ensembles, published music books, and produced Grammy-nominated albums as part of a resolute four-decade campaign to promote the legacy of her late husband, the brilliant and mercurial composer, bandleader, and double bass virtuoso Charles Mingus, died Saturday at a hospital in Manhattan. She was 92.

Her death was confirmed by her son, Roberto Ungaro, who said she had been in declining health but did not give a specific cause. She died 15 years to the day after the death of her brother Richard A. Graham, a founder of the National Organization for Women and an inaugural member of the federal Equal Employment Opportunity Commission.

A former Midwestern debutante who rebelled against her conventional upbringing — her friends included poet Allen Ginsberg as well as literary critic Harold Bloom — Ms. Mingus often downplayed the impact of her years championing her husband’s music and image. “Charles’s music is Charles’s music,’’ she told The Washington Post in 1999, two decades after he died of a heart attack at age 56. “I may have speeded the process up,’’ she continued, referring to a composer whose songs were recorded by artists including Leonard Cohen, Joni Mitchell, and Keith Richards, “but that’s all.’’

Yet to many jazz historians and musicians, she played a crucial role in shaping the legacy of her husband, whose music combined traditional blues and gospel with complex harmonies, free-ranging melodies, and an abiding love of collective improvisation. His popularity rose and fell during his lifetime as he battled depression, alienated audiences and collaborators with his fits of rage, and struggled with amyotrophic lateral sclerosis.

“If it hadn’t been for Sue Mingus, his music would not be as revered as it is today,’’ journalist and critic Nat Hentoff once told the Post. “What she has done is keep Mingus’s music alive, literally.’’

As Ms. Mingus told it, she knew virtually nothing about jazz when she met her husband in 1964 while seeing him in concert. She was acting in an underground film directed by Robert Frank, “O.K. End Here,’’ which was supposed to feature a soundtrack from saxophonist Ornette Coleman. A friend working on the film decided to introduce her to the city’s jazz scene and brought her to the Five Spot in Lower Manhattan, where she took a seat at the bar during intermission and sipped a gin and tonic while watching as Mingus ate alone at his table, “as intense and private as a holy man meditating on his chakra.’’

“I liked him immediately,’’ she wrote in “Tonight at Noon: A Love Story’’ (2002), a memoir about their relationship. “I liked his aloneness in the tumultuous room, his concentration on the outsized beef bone at hand.’’

When Mingus came over to grab a bottle of wine, she asked him whether he had seen Coleman, and then explained that the musician was writing music for a movie she was in. “You in a movie?’’ Charles replied with surprise. “With those teeth?’’

They soon struck up a relationship. After a few years, she recalled, they were “married’’ by Ginsberg, a Buddhist who presided over an impromptu ceremony by chanting at the couple for more than an hour. They were legally married in 1975 — it was Charles’s fourth marriage and Ms. Mingus’s second — this time by a justice of the peace.

By then, Charles had started contributing to Changes, a New York arts magazine founded by Ms. Mingus, while she booked his tours and helped with his music publishing company. After his death in 1979, she traveled to India and, at his request, scattered his ashes in the Ganges River. When a tribute concert was organized in his honor later that year, she assembled a band called Mingus Dynasty, featuring musicians who had played with him during his lifetime, including drummer Dannie Richmond and trombonist Jimmy Knepper.

“I had no idea what I was doing,’’ she told The New York Times in 2007, recalling that she pieced together the ensemble by calling musicians credited on the back of his albums. The group went on to perform at jazz festivals across the country and served as a template for later ensembles formed by Ms. Mingus, including the 10-piece Mingus Orchestra.

Collaborating with musicologist Andrew Homzy and the composer and conductor Gunther Schuller, she produced the 1989 Lincoln Center premiere of Mingus’s monumental composition “Epitaph,’’ using a 500-page, 15-pound score that was located and stitched together after his death. Musicians from Mingus Dynasty and the “Epitaph’’ orchestra were then chosen for the Mingus Big Band, a 14-piece ensemble that she created to ensure his music was regularly performed.

To Ms. Mingus’s surprise, the group became a New York institution, initially playing weekly gigs at Fez Under Time Cafe. “There’s really no explaining the popularity,’’ she told the Times in 1994, three years after forming the group. “But I think Charles would be tickled.’’

Somewhat like her husband, Ms. Mingus could be testy toward the group’s musicians, teasing them at times for playing too loudly or soloing too long. But in general, “she treated her musicians as her extended family,’’ her son said in a phone interview, and drew praise from music critics for the lineups she assembled and the albums she produced, including the Mingus Big Band’s Grammy-winning “Live at Jazz Standard’’ (2010).

“When someone like Glenn Miller or Artie Shaw dies and a sideman takes over the band, it’s called a ghost band because it just isn’t the same,’’ Hentoff said in 1999. “But with the Mingus Big Band — and I’m not exaggerating — you can feel Mingus. It’s because of Sue. She knows what musicians to choose, she knows who understands the music.’’

The oldest of three children, she was born Sue Graham in Chicago on April 2, 1930. She grew up in Milwaukee, where her parents filled the home with classical music.

Ms. Mingus was educated at all-girls schools, and after graduating from Smith College in 1952, she moved to Paris to work as a journalist. She eventually landed a job in Rome at the in-flight magazine for Pan Am and married an Italian sculptor, Alberto Ungaro, before returning to New York with her husband in 1958. They separated after a few years.

After Charles Mingus’s death, Ms. Mingus helped organize his papers and donated his archives to the Library of Congress. She also published books including “Charles Mingus: More Than a Fake Book’’ (1991), which included 55 of his original scores; produced a documentary, “Charles Mingus: Triumph of the Underdog’’ (1998); and campaigned against bootleggers who released pirated recordings of her husband’s concerts. At times she stole bootleg albums from record stores, eventually launching her own music company, Revenge Records, to reissue recordings of his concerts.

Ms. Mingus started a nonprofit organization, Let My Children Hear Music, to promote her educational efforts, which grew to include an annual festival and high school jazz competition.