Mr. Klein, who was one of the most powerful figures in the music business in the 1960s but ended up feuding with some of his biggest clients, died at his New York home of Alzheimer's disease, said Bob Merlis, publicist for ABKCO Music & Records.

An accountant known for his brashness, temper, and tenacity in tracking down royalties and getting better record deals, Mr. Klein garnered clients including Sam Cooke, Bobby Darin, and Herman's Hermits.

But he became most famous - and later infamous - for signing on the Rolling Stones and then the Beatles. Both arrangements eventually spurred lawsuits, with some Beatles fans blaming Mr. Klein for contributing to the tensions that broke up the group.

Mr. Klein was convicted of tax fraud in 1979 and served two months in prison for failing to report income from sales of promotional records by the Beatles and other groups; the records were supposed to be given away. The Rolling Stones grew so infuriated with Mr. Klein - whose company still owns an enormous chunk of their 1960s songs - that Mick Jagger once chased him down the hall of a posh hotel.

Regardless, Mr. Klein remained "very proud of the position he was in and what he was able to do with the different artists he was able to work with," Merlis said.

Mr. Klein began building his reputation by auditing record companies' books and finding unpaid royalties for Darin and other artists. After meeting Cooke in 1962, he helped the soul singer secure a then-unusual level of control over his music and finances.

"I never wanted to be a manager," he told the Star-Ledger of Newark, N.J., in 2002. "It was going over the books that I loved. And I was good at it."

That helped him win over the Rolling Stones, who hired him in the mid-1960s. He helped the group negotiate a new contract with its label, but the relationship soured after Mr. Klein bought the rights to the band's 1960s songs and recordings from a former manager.

He was fired in 1970, but the animosity continued for years, culminating in dueling lawsuits over rights and royalties and a 1984 trial. Jagger testified in a federal court in New York that Mr. Klein "wanted a hold on us, on our futures" - and that a 1974 discussion about money ended with a shouting Jagger chasing Mr. Klein down a corridor at London's Savoy Hotel. The lawsuit was settled soon after, with Mr. Klein keeping the song rights but agreeing to pay royalties promptly.

Mr. Klein bought a controlling interest in the Cameo-Parkway record label in July 1967. The Beatles' longtime manager, Brian Epstein, died that year, and Mr. Klein, whose sights had long been set on managing the Fab Four, saw his chance.

Initially rebuffed, Mr. Klein eventually won John Lennon's favor.

"He not only knew my work, and the lyrics that I had written, but he also understood them, and from way back. That was it," Lennon told an interviewer in 1970.

The group hired Mr. Klein in 1969 over the objections of Paul McCartney, who preferred his father-in-law, Lee Eastman.

At the time, a New York Times profile referred to Mr. Klein as "the toughest wheeler-dealer in the pop jungle." But his relationship with the Beatles was bitter and short-lived.

The group broke up the next year, and McCartney sued his bandmates in an effort to break free from Mr. Klein. McCartney went on to revile Mr. Klein in a 1997 biography, Paul McCartney: Many Years From Now.

The other Beatles lost faith in Mr. Klein, leading to lawsuits and countersuits in the mid-1970s. Lennon sent him off in song in "Steel and Glass," which describes how "your mouthpiece squawks as he spreads your lies."

Mr. Klein was born in Newark and spent several years in an orphanage after his mother's death during his infancy. He was later raised by a grandmother and an aunt.

Mr. Klein graduated from Upsala College and served in the U.S. Army before joining a Manhattan accounting firm, according to his company.

He started his own firm, which later became ABKCO, in the late 1950s. Besides managing music, he co-produced 1971's The Concert for Bangladesh, a forerunner of today's charity concerts, and films including 1978's The Greek Tycoon, starring Anthony Quinn and Jacqueline Bisset.