The Canadian baritone saxophonist and composer played with many of the U.K.'s most notable modernists beginning in the ‘60s, including the pianist John Taylor, saxophonists John Surman and Alan Skidmore, and composer/pianist/bandleader Mike Westbrook. Warren was musically self-taught before entering the McGill University Conservatory in the late ‘50s. Warren led his own band in England beginning in 1968; at various times the group included Surman, Skidmore, Taylor, flugelhornist Kenny Wheeler, and saxophonist Ray Warleigh, among others. Warren played in Westbrook's Concert Band from 1967-76, recording with the group such albums as Marching Song Vol. 1&2 (Deram and Metropolis (BGO Records). With Surman, Warren recorded his composition Tales of the Algonquin (Deram in 1971. He also toured with the London Jazz Composers Orchestra in 1972, and conducted and composed for Surman's Brass Project in the ‘80s.