The album is often considered within the canon of psychedelic rock. The "Encyclopedia Britannica" states that the Beach Boys introduced psychedelic elements with the album, calling it "expansive" and "haunting". Although Vernon Joyson felt the album contained acid rock gestures, he chose to omit the Beach Boys and "Pet Sounds" from his book "The Acid Trip: A Complete Guide to Psychedelic Music" on the basis that they "essentially predated the psychedelic era." Bret Marcus of "Goldmine" believed that the album is psychedelic pop, even though most people hesitate to name the Beach Boys in discussions of psychedelic music. Stebbins writes that the album is "slightly psychedelic—or at least impressionistic." Psychedelic qualities that were common in the group's mid-1960s work were the invocation of "greater fluidity, elaboration, and formal complexity", "a cultivation of sonic textures", "the introduction of new (combinations of) instruments, multiple keys, and/or floating tonal centers", and the occasional use of "slower, more hypnotic tempos".