Gilbert Kaplan, 74

Gilbert E. Kaplan, who made his fortune as a publisher in the financial world but gained international renown for conducting Mahler’s Second Symphony, died on New Year’s Day in Manhattan of cancer, at 74. He had been diagnosed in October.

Mr. Kaplan began his financial career as an economist with the American Stock Exchange. In 1967, having noted that professional investors did not have a publication devoted to their field, he borrowed $150,000 to launch the monthly magazine Institutional Investor. It quickly turned a profit, and he found himself a self-made millionaire at the age of 27. He remained its editor-in-chief after selling the by-then multimedia company in 1984 to Capital Cities Communications for what was reported to be over $70 million.

His dedication to the Mahler Second began in 1965 when a friend invited him to a rehearsal of the symphony at Carnegie Hall. Leopold Stokowski was the conductor, and the experience was a life-changer. “I felt like a bolt of lightning had gone through me,” he told The Star in 2001. “The music just seemed to wrap its arms around me and never let go.”

 By the time of his death, he had led 60 orchestras in the work, among them the Vienna Philharmonic, New York Philharmonic, Deutsche Oper Berlin, Bavarian Radio Symphony Orchestra, London Symphony, Royal Philharmonic, St. Petersburg Philharmonic Orchestra, Russian National Orchestra, Moscow State Symphony Orchestra, Los Angeles Philharmonic, and the Philharmonic Orchestra of La Scala. The London Symphony Orchestra’s performance of the Second, with Mr. Kaplan on the podium, is the best-selling recording ever made of the work.

He first conducted it in 1982 with 119 members of the American Symphony Orchestra, before an audience of some 2,500 invited guests at Avery Fisher Hall, which he had rented. He had studied it for 17 years, putting in long hours working here in East Hampton with a known conductor and traveling to rehearsals and performances from Missouri to Melbourne. Over the years, he would make a short speech, which he had memorized in 18 languages, before each of his performances. He was able to conduct the work from memory, using a baton that had belonged to Mahler himself.

Although some critics remained skeptical that a person with little musical experience could achieve greatness as a conductor, Mr. Kaplan received extraordinary praise from the start. His very first performance, said The Village Voice’s critic, was “one of the most profoundly realized Mahler Seconds in the last 25 years.”

Acknowledging that he was an amateur, Mr. Kaplan limited performances to three a year and never accepted a fee.

In 2008, when he conducted a performance in Manhattan by the New York Philharmonic, The New York Times critic Steve Smith wrote that “every gesture had purpose and impact, and the performance as a whole had an inexorable sweep. To think there is nothing else to know of Mahler’s Second beyond what Mr. Kaplan has to show would be a mistake. But it seems likely that no one is better equipped to reveal the impact of precisely what Mahler put on the page.”

In fact, Mr. Kaplan had become a scholar not only of Mahler’s music but of his life. He was able to buy the original manuscript of the Second, telling an interviewer that seeing the composer’s handwritten notes made it possible for him to follow his intentions more precisely. He also collected memorabilia and lectured frequently on Mahler, doing so to a full house at Guild Hall in East Hampton on April 19, 2014.

Mr. Kaplan and the former Lena Biorck, who survives, met at Georgica Beach in East Hampton, where, for the rest of his life, he took daily walks whenever possible, with her or some of their four children. A recent family Christmas card contained a photo taken there.

The family house on Apaquogue Road in East Hampton was purchased in 1969. Mr. Kaplan, who enjoyed diving, had one-meter and three-meter diving boards installed at the pool and for several years invited Olympic divers such as Greg Louganis and their mutual coach Ron O’Brien to display their skills and attend parties, including one at which everyone wore white. For the most part, though, Mr. Kaplan led a quiet life here, going with his children to the Clam Bar on Napeague or the Palm restaurant in East Hampton Village for a steak.

Norman Lebrecht, who wrote about an early performance for the London Sunday Times and later became a close friend, said, “He was a lovely man: warm, funny, loyal, and brave. I spent time with him last month and treasure every moment of our friendship, which lasted half my life.’

Mr. Kaplan conducted the Choral Society of the Hamptons in the final movement of the Mahler Second Symphony twice. In order for the group to perform it, he re-orchestrated it, terming the finished work a chorale. The full, five-movement, 90-minute symphony calls for more than 100 instruments and a huge chorus; here it was performed by 22 instrumentalists and some 50 choristers. Mr. Kaplan told the Star interviewer that it had been fascinating to arrange the work for a chamber ensemble.

The Kaplans are art collectors as well, owning works by Dali, Miro, Picasso, Man Ray, and Magritte, whose paintings Mr. Kaplan had cataloged, as well as a bust of Mahler by Rodin. Mr. Kaplan told The Star that “if you define Surrealism as . . . ‘that point where the real and unreal meet’ there is much in Mahler’s music that can meet this definition.”

He was born in Manhattan on March 3, 1941, and grew up on Long Island, in Lawrence. He had piano lessons for a few years as a child, the extent of his musical training. He attended Duke University, transferring to the New School for Social Research in Manhattan, where he obtained a bachelor’s degree, and attending New York University Law School.

In addition to his wife, Mr. Kaplan is survived by his children, Kristina Wallison and Claude Davies, both of New York, and John Kaplan and Emily Kaplan, both of Los Angeles, and by eight grandchildren. A brother died before him.

The family received friends at the Frank E. Campbell Funeral Chapel in Manhattan last Thursday. He was buried at Oakland Cemetery in Sag Harbor on Saturday. The family said they would have a memorial, ”with much music,” in the spring.

Mr. Kaplan addressed the unusual tacks his life was taking in an op-ed in The New York Times in 1983, writing: “We all have dreams and there is no question that one of life’s great tragedies is that so few of us fulfill them . . . it’s a lack of nerve, an unwillingness to take the necessary risks.” Mr. Kaplan took those risks and fulfilled his dreams.