Joan Ingpen, who died on December 29 at 91, was a legendary figure among opera impresarios who co-founded the Philharmonia with Walter Legge; introduced the musical world to Georg Solti, Luciano Pavarotti, and Joan Sutherland; and played major casting and administrative roles at three of the world’s leading opera houses: Covent Garden, Paris Opera, and the Met in New York. She was a walking index of opera singers, knowing who could sing what, who was scheduled to sing what, and who might be available and when. Although she kept lists on faded legal pads and introduced computerized planning at the Met, most of her knowledge was kept in her mind.

It was in 1963, while working at the Royal Opera, that Ingpen heard Pavarotti in Verdi’s “Rigoletto” at the Dublin Grand Opera Society. She hired him as understudy for the ailing Giuseppe di Stefano as Rodolfo in “La Boheme” with the promise of a Covent Garden debut in the final performance. In the event, Pavarotti sang all but the first of the 27 shows, launching a career that lasted until his death last year. One of her last – and happiest — finds, she said, came in the mid-1980s when she “discovered” Anne Sofie von Otter.

Ingpen’s legacy will be Ingpen & Williams, the management agency that she founded in 1946. The most prominent London concert promoter at that time was Ibbs & Tillett, and Ingpen felt that any respectable impresario should similarly have a double name, giving the impression of being a solid partnership. But, being unable — or unwilling — to find anyone to work with, she took the name of her dachshund, Williams. This arrangement had the distinct advantage of the dog being unable to answer back.

Georg Solti was one of the artists she introduced to Britain, having worked with him in an armed forces’ entertainment unit during World War II. Joan Sutherland, whom Joan Ingpen first heard as a student in 1951 at the Royal College of Music, was another.

Change came in 1961 when, having secured for Solti the post of musical director at Covent Garden, Ingpen joined him as controller of opera planning.

She began making long-term plans with Solti, and became known as one of the few people able effectively to deal with the fiercely impatient musical director. “We called him Soltissimo, because he always wanted everything yesterday,” she noted.

Solti left Covent Garden in 1971, and the two were reunited at the Paris Opera, where she continued in much the same vein as she had in London, until Placido Domingo persuaded James Levine to bring her to the Metropolitan Opera in 1981. The Met was recovering from a bitter industrial dispute. It was not to be a happy assignment, with the New York Times describing Joan Ingpen as “a martinet with an obsession with fixing casts in cement for years in advance.” It also was not long before she encountered difficulties in pinning down the notoriously vague Levine, then the Met’s music director. The Swiss conductor Peter Maag considered her to be “cavalier.” After three years she was not sorry to return to Europe with the role of “liaison officer and talent-scout” for the Americans.

Joan Ingpen was a formidable character, with a razor-sharp memory, a remarkable eye for detail and — at times — an icy smile. She could be a powerful negotiator when discussing casting or negotiating a singer’s fee. Her affection for opera singers was plain for all to see, and she would accept only the very best from them. “I really love them,” she once said. “But, of course, they tend to be more highly strung than actors because everything depends on those two little vocal cords and their life is a perpetual worry.”

Joan Mary Eileen Ingpen was born on January 3, 1916, in London of Irish stock. Her father was said to have been sent on a mission to Russia just before the Bolshevik revolution, and was never seen again. Although she was a competent pianist, young Joan learned to type and began her working life in the office of a marine insurance broker. Much of her social life in London was taken up with concerts. It was at one of these that she met Walter Legge from EMI, and after working together during the war, they co-founded the Philharmonia. As the orchestra’s reputation grew, Legge was anxious to steal the limelight, and they fell out bitterly. In 1950, Legge bought out her share in the orchestra and they went their separate ways.

Fortunately, Ingpen had established her agency in 1946, and now gave it all her energy. She could be as much prima donna as any of her clients. On one occasion Pavarotti is said to have kept her waiting in his living room while he cooked pasta and took phone calls; she is said to have retaliated by keeping him off the stage at the Met for a year. On another she publicly denounced as “canary fanciers” that vociferous section of the Met’s audience, which insists on seeing ageing singers return beyond their prime.

Today Ingpen & Williams remains a leading player in classical music management, with a roster of artists that includes Pierre Boulez, Alfred Brendel, and a host of well-known singers.

In retirement Ingpen lived quietly in an apartment in Brighton, where she kept a Hockney design for a triple bill at the Met— Parade, Les Mamelles de Tiresias, and L’Enfant et les Sortileges — adorned with the letters JOAN.