The Doors emerged amid the turbulence of the late Sixties with music that was as intense and complex as the times that spawned them. They derived their name from references to "the doors of perception" in works by William Blake and Aldous Huxley. The group's dark, brooding personality came largely from singer Jim Morrison. Musically, the other members of the Doors—keyboardist Ray Manzarek, guitarist Robby Krieger and drummer Jon Densmore—combined classical rigor with freewheeling, jazzy improvisations, providing Morrison a platform from which to declaim his poetical lyrics in a portentous baritone. The source of Morrison's intensity was addressed in an early interview: "It's the feeling of a bowstring being pulled back for twenty-two years and suddenly let go." When they weren't performing original songs about sex, death and the unknown, the Doors would occasionally transform old blues numbers, such as Willie Dixon's "Back Door Man" and John Lee Hooker's "Crawling King Snake."