The cause was a heart attack, said his wife, Lori Chapman. He had been undergoing dialysis treatment for kidney problems for several years, she said.

Mr. Harrison was the son of the English actor Rex Harrison, a star of "My Fair Lady" and "Doctor Dolittle," and the first of his father's six wives, Collette Thomas. He initially resisted acting, he said, because he wanted to distance himself from his father's reputation.

"I always regarded it with awe and trepidation," he told The Los Angeles Times in 1968. "Because, I suppose, my father is a famous actor."

Mr. Harrison focused instead on music and skiing, competing on England's alpine ski teams at the 1952 and 1956 Olympic Games and singing folk and calypso songs in nightclubs around Europe. He often performed at the Blue Angel in London, where he was encouraged by a young Paul McCartney.

Mainstream success eluded him, so he moved to the United States in the mid-1960s. His first hit was "A Young Girl," an English version of Charles Aznavour's French ballad; it reached No. 51 on the Billboard Hot 100 in 1965. He recorded albums that included Beatles and Bob Dylan songs and appeared on "The Ed Sullivan Show" and other television shows.

He was also cast as Mark Slate, a secret-agent sidekick to April Dancer, played by Stefanie Powers, in "The Girl From U.N.C.L.E.," a spinoff of "The Man From U.N.C.L.E." The show was canceled in 1967, but it raised Mr. Harrison's profile. He went on to perform with the Beach Boys and Sonny and Cher and to appear on shows like "The Mod Squad" and "Mission: Impossible."

He recorded "The Windmills of Your Mind," composed by Michel Legrand with lyrics by Alan and Marilyn Bergman, in 1968. Heard on the soundtrack of the film "The Thomas Crown Affair," it won the 1968 Oscar for best original song.

The song did not initially make an impression on Mr. Harrison.

"I went to the studio one afternoon and sang it and pretty much forgot about it," he wrote on his Web site. "I didn't realize until later what a timeless, beautiful piece Michel Legrand and the Bergmans had written." Mr. Harrison missed the chance to perform the song at the Academy Awards ceremony because he was in England filming "Take a Girl Like You," a comedy based on a novel by Kingsley Amis. (José Feliciano sang in his place.)

He said he never tired of the song, and performed it in his final concert, in Black Dog, England, the Saturday night before he died.

Noel John Christopher Harrison was born in London on Jan. 29, 1934. His parents divorced in 1940, and he left school as a teenager to ski in the Swiss Alps.

He lived in Los Angeles during the peak of his career, but left in the early 1970s for a farm in Nova Scotia. While there he hosted "Take Time," a music show for the Canadian Broadcasting Corporation.

He returned to Los Angeles for the tour of his one-man show, "Adieu, Jacques ... ," about the singer Jacques Brel, before moving back to England. At his death he lived in Ashburton, in southwest England.

Mr. Harrison's first two marriages, to the former Sara Tufnell and Margaret Harrison, ended in divorce.

In addition to Ms. Chapman, he is survived by two daughters, Cathryn Harrison-Laing and Harriet Harrison-Roger; a son, Simon; and a stepdaughter, Zoe Humphreys, from his first marriage. He is also survived by a son, Will, and a daughter, Chloe Harrison-Bayes, from his second marriage; two half-brothers, Carey Harrison and Richard Butler; and four grandchildren.