Lyle Mays, a jazz keyboardist whose work, chiefly with the Pat Metheny Group, won nearly a dozen Grammy Awards, died Feb. 10 in Los Angeles. He was 66.

The death, of unspecified causes, was announced on Pat Metheny’s website.

He co-founded the Pat Metheny Group with guitarist Metheny in the 1970s, where he was a performer, composer and arranger. The group’s fusion style incorporated rock, contemporary jazz and world music.

The group won jazz fusion performance Grammys, and some for best contemporary jazz album, including 2005’s award for “The Way Up.” But the group also scored an award in 1998 for best rock instrumental performance for “The Roots of Coincidence.”

Mr. Mays also was a sideman for albums by jazz, rock and pop artists, including Joni Mitchell, Rickie Lee Jones and the group Earth, Wind & Fire. He helped compose soundtrack music for several movies, including “The Falcon and the Snowman” (1985).

Lyle David Mays was born in Wausaukee, Wis., on Nov. 27, 1953. His mother and father played piano and guitar, and he played organ as a youngster.

Mr. Mays, who cherished the technical and analytical aspects of his craft as well as the improvisational part, also was a self-taught computer programmer and architect who designed a house for a relative.