"Sheep" ties up the concept of 1977's Animals quite nicely. Within the story line of the song, the sheep (representing the oppressed and the manipulated masses in society) rise up and revolt against the powerful dogs who attempt to take advantage of them and exploit them. Almost led to slaughter, the sheep form a silent union to overtake the corruptive dogs, realizing that they have been ill-treated, subservient, and tyrannized for too long. Beginning with the peaceful sounds of sheep grazing and birds singing, the song then erupts with Waters' explosive voice, a feat Gilmour admitted he could never recapture if he sung it himself. The song was originally called "Raving and Drooling" when performed in its early stages throughout their Dark Side tour, but was changed to keep the song titles as animal names. Within the middle of the song, an altered form of the 23rd Psalm (The Lord is my shepherd...) is heard, although it's hard to make out since it is spoken through a Vocoder, but it goes on to illustrate how the sheep have rebelled against the evil dogs. The instrumental aspects of the song involve Rick Wright playing some impressive Hammond organ work, capturing the serenity of the grazing sheep and filling in behind Gilmour's guitar throughout the song. Gilmour's guitar playing is quite impressive in itself, conjuring up the frantic scene of the mighty sheep's backlash with some feverish string bending. "Sheep"'s use of the organ reflects Floyd's early sound of the late '60s but only slightly, as it quickly switches into a straight-ahead rock song which carries the underlying message of Animals clearly throughout its lyrics.