Mr. Leonard, who was born Aug. 16, 1931, in Rockville Centre, Long Island, was a piano prodigy and when he grew up his musical interested ranged widely. He did musical arrangements for jazz pianist Bill Evans, and wrote music for television shows such as "Happy Days."

He did some musical arrangements for the 1959 Pearl S. Buck play A Desert Island, which ran just a week. In 1965, he returned to Broadway as the composer of The Yearling, a musical based on the novel by Marjorie Kinnan Rawlings. The lyrics were by Herbert Martin, and the book was by Martin and Lore Noto. Lloyd Richards directed. It ran just a weekend, but the show’s profile was raised considerably when Barbra Streisand later recorded four of the score’s songs.

How to Be a Jewish Mother, a 1967 play with music (again written with Martin), starring Molly Picon, didn’t do much better. But Mr. Leonard scored a big success with Grease, in which he orchestrated the music of Jim Jacobs and Warren Casey. The show ran for eight years and became a cultural phenomenon.

Mr. Leonard’s songs were recorded by a wide variety of singers, including Marvin Gaye, Johnny Mathis and Julie Wilson. Bill Evans recorded two Yearling songs on his album "From Left to Right." Later, Mr. Leonard referred to his collaboration with Evans as "the highlight of my life."

In her 1987 solo Broadway show, Barbara Cook sang his Yearling song "Why Did I Choose You?." A revue of his music, Words Fail Me, was staged by the Penguin Rep in Stony Point, NY, in 1990.

Michael Leonard studied classical music at Juilliard and the Handel Conservatory in Munich. In 1960, Mr. Leonard conducted for the singer Dick Haymes. Later, he served as musical director for Tommy Sands.