Gilbert E. Kaplan, a financial publisher who had an accidental second career as an international symphony conductor — despite the fact that he could scarcely read music and possessed a concert repertoire of exactly one piece — died on New Year’s Day in Manhattan. He was 74.

The cause was cancer, his daughter Emily Kaplan said.

Originally trained as an economist, Mr. Kaplan was the founder and longtime chief executive of Institutional Investor, a monthly magazine for pension fund and asset managers. After starting the publication in 1967, at 26, he built it into a multimedia concern comprising magazines, journals, conferences and other services. He sold the company in 1984 for a figure reported to exceed $70 million.

By then, Mr. Kaplan had embarked on his unlikely vocation as a globe-trotting conductor of Mahler’s Second Symphony — and only Mahler’s Second Symphony. That work, which had held him in thrall for years, would propel him onto the podiums of some of the world’s leading orchestras, including the Vienna Philharmonic, the London Symphony, the Los Angeles Philharmonic, the St. Louis Symphony and, in an outing that became the subject of a headline-making fracas, the New York Philharmonic.

For an untrained conductor to lead a symphony orchestra — much less to lead one in a fiendish piece like Mahler’s Second — is, as The St. Louis Post-Dispatch wrote in a 1991 review of one of Mr. Kaplan’s concerts, “almost preposterous.”