NEW YORK (NYT NEWS SERVICE ).- Lyle Mays, a keyboardist, composer and arranger best known for his long association with guitarist Pat Metheny, died Monday in Simi Valley, California. He was 66.

His death, at Adventist Hospital, was announced by his niece Aubrey Johnson, a jazz singer. She did not specify the cause, saying only that he died “after a long battle with a recurring illness.”

Metheny has long been one of the marquee names in jazz. But the albums he made with his working band from 1978 to 2005 for ECM, Geffen and other labels were always credited to the Pat Metheny Group, never just to Metheny. And Mays was an integral part of that lean quartet from its early days, whether giving depth and color to its sound on synthesizers or soloing gracefully on grand piano.

The group gained fame by merging jazz ideas with a rock sensibility; its later incarnation as a larger ensemble incorporated musical ideas from other parts of the world, notably Brazil.

He also wrote, in collaboration with Metheny, many staples of the group’s repertoire, among them “San Lorenzo,” “American Garage” and “James.”

The personnel of the Pat Metheny Group changed several times over the years. Besides its leader, Mays was the band’s only constant.

“Lyle was one of the greatest musicians I have ever known,” Metheny said in a statement on his website, adding, “From the first notes we played together, we had an immediate bond.”

His contributions to the Pat Metheny Group earned Mays 11 Grammy Awards. For his work both with Metheny and on his own, he had a total of 23 Grammy nominations.

Lyle David Mays was born Nov. 27, 1953, in Wausaukee, a village in eastern Wisconsin. His parents encouraged his interest in music and were musically inclined themselves. His father, Cecil, a truck driver, taught himself to play guitar; his mother, Doris (Olson) Mays, who worked in a bank, played piano and organ in a local church.

Mays himself began playing organ in church at 9 and developed an interest in jazz not long afterward. After attending the University of Wisconsin-Eau Claire, he transferred to North Texas State University (now the University of North Texas), where he played piano in the school’s celebrated One O’Clock Lab Band while composing and arranging its music. He wrote all the compositions and arrangements on the band’s Grammy-nominated album “Lab 75.” He left in 1975 to tour with Woody Herman’s big band.

Mays met Metheny in 1974 at the Wichita Jazz Festival in Kansas. They first recorded together in 1977 on Metheny's album “Watercolors” and formed the Pat Metheny group shortly afterward. The group's first album, released the next year, was titled simply “Pat Metheny Group.”

Their other ventures included writing the score for the John Schlesinger spy thriller “The Falcon & the Snowman” (1985), starring Sean Penn and Timothy Hutton. That score included a collaboration with David Bowie, “This Is Not America,” which was a Top 40 hit.

Mays and Metheny released one album as co-leaders, the atmospheric and whimsically named “As Falls Wichita, So Falls Wichita Falls” (1981). Reviewing it for The New York Times, Stephen Holden called it “a winning combination of electronic innovation and neo-Romantic lyricism,” and noted that Mays “dominates the record.” In a recent Facebook post, the bassist Christian McBride, another longtime Metheny associate, called it “one of the most moving documents of pure beauty ever made.”

Mays is survived by two sisters, Joan Johnson and Jane Tyler.

Mays also performed or recorded with Joni Mitchell (on her “Shadows and Light” tour and album), Bobby McFerrin, Rickie Lee Jones and others. He recorded a few albums as a leader, among them “Fictionary” (1992), a trio recital with Marc Johnson on bass and Jack DeJohnette on drums, and “Solo: Improvisations for Expanded Piano” (2000).

His last recording with the Pat Metheny Group was “The Way Up,” released in 2005. He stopped making music professionally in 2011, although, he said in a 2016 podcast interview for the magazine Jazziz, “I kind of feel like the music industry has left me.” In recent years he worked as a software consultant.

Among his other nonmusical pursuits, Mays was a self-taught architect. His designs included a house for his sister Joan.

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