[1] Warren studied saxophone and flute during his university years, and his initial forays into composition were encouraged by the celebrated Canadian trumpet player, Herbie Spanier, leading to early performances of his work on CBC radio and TV.
The 1970s marked a productive period for Warren, with the recording of his suite Tales of the Algonquin and compositions for the John Surman Octet, the Alan Skidmore Quintet, and vocalists Norma Winstone and Karin Krog.
During this decade, Warren also delved into arranging Chet Baker's solos with lyrics by Georgie Fame for performances with the NDR Big Band.
He also revisited his earlier work, performing Tales of the Algonquin with the Bohuslän Big Band and presenting the suite with the AltSys Jazz Orchestra in Montreal.
In 2019, Warren's composition The Traveller's Tale was performed by John Surman and The Brass Project at the EFG London Jazz Festival, followed by the release of a live recording of the piece.