Mitch Leigh was a composer who got his start writing advertising jingles and went on to achieve international acclaim as the composer of the classic musical Man of La  Mancha.

Born in Brooklyn, New York, Leigh graduated from the High School of Music and Art in Manhattan. After serving in the Army he used the G.I. Bill to attend Yale University, where he earned bachelor’s and master's degrees in music.

He found work in the world of New York advertising and wrote jingles for such clients as  L & M cigarettes, Ken-L Ration dog food and Sara Lee. In 1964, while working in the ad world, was offered the opportunity to write songs for a musical based on Miguel de Cervantes's Don Quixote.

Despite limited experience in the musical theater, Leigh achieved a kind of immortality with the play, Man of La Mancha. His music for the production proved to some of the most enduring in the genre, especially "The Impossible Dream," an anthem of optimism and perseverance that has been recorded by some of the finest singers of the past 60 years, including Frank Sinatra, Plácido Domingo and Jacques Brel. The show, which starred Richard Kiley, opened in New York in 1965 and ran until 1971 — 2,328 performances. It won five Tony Awards, including best composer and lyricist (for Leigh and Joe Darion) and best musical. It has been performed throughout the world and inspired a 1972 film starring Peter O’Toole.

Music from the show, most frequently "The Impossible Deam," has appeared in dozens of television programs, including The Ed Sullivan Show, The Smothers Brothers Comedy Hour, Petticoat Junction, Rhoda, The Muppet Show, Quantum Leap and Behind the Candelabra.

Leigh died March 16, 2014, in New York City. He was 86.