In the 1950s, when jazz clubs dotted Los Angeles, Mr. Niehaus was a fixture on the scene, alongside other legendary musicians including Chet Baker, Hampton Hawes, Shorty Rogers and Bill Holman.
But it was on the road with Stan Kenton’s band that Mr. Niehaus rose to national prominence as the bandleader’s dynamic alto saxophonist for years. When crowds dwindled in the 1960s as rock music took over the airwaves, Mr. Niehaus turned to Hollywood and, ultimately, Eastwood.
Leonard Niehaus was born on June 11, 1929 in Saint-Louis and grew up in a family of musicians. Her father played the violin and her sister eventually became a concert pianist. He started playing the clarinet at age 13 but gave it up in favor of alto sax when he began to listen to the contagious sounds of big band jazz.
Mr. Niehaus completed high school in Los Angeles and studied music at what is now California State University in Los Angeles, graduating with the school’s inaugural class in 1951.
Determined to make his way as a working musician, he joined Kenton’s band but had to quit when he was drafted into the army. When he was released, he joined Kenton’s band for another five years, until it became clear that the musical landscape was changing.
“I put my horn away and started writing instead,” Mr. Niehaus told the Los Angeles Times in 2000.
He found steady work in Hollywood, writing scores for shows such as “Charlie’s Angels” and “McMillan & Wife.” His career blossomed when he reconnected with Eastwood, whom he met while stationed in Fort Ord in Northern California. They shared a love of jazz.
Perhaps the most resonant film was the 1988 biopic “Bird,” about jazz saxophonist Charlie “Bird” Parker. Mr. Niehaus created new musical backgrounds for Parker’s classic solos and taught the film’s star, Forest Whitaker, how to play the alto saxophone.
Mr. Niehaus won an Emmy Award for composing the 1993 TV movie “Lush Life” starring Whitaker and Jeff Goldblum. His last film project with Eastwood was for “J. Edgar,” a biopic about former FBI director J. Edgar Hoover.
“Lennie is great because when a movie dictates something simple, he’ll keep it simple or make it complicated when he demands it,” Eastwood told The Times in 1998. “He’s so versatile and smart about the relationship from music to film. that I’ve used it on almost every project I’ve done.
Mr. Niehaus then hosted a concert at Carnegie Hall, eventually released as a live album, which paid homage to Eastwood’s cinematic legacy. He also continued to play his saxophone on occasional recordings and in appearances at clubs and other venues, including a bookstore near his home in Southern California.
“It’s just what I do,” he said.
Survivors include his wife, Patricia; a girl; and two grandchildren.