You'll notice among many metal acts a bent for the scatological. Though more pronounced in the lyrics of eternal sophomores like Abscess, who sing of cannibal autopsies and pornographic freak shows, this tendency is also readily observed in the subject matter and packaging of Tool. They've praised man-on-man prison rape ("Prison Sex") and hidden a photo of a cow licking its own ass in the Undertow album. A grooved-plastic cover on the latest, Aenima, brings hazy, insertable cards to unsavory life, including a picture of band members in various states of undress on a couch salivating over a naked contortionist. All of which is to say: Nicely done! Because whether you find this sort of thing offensive or not, if you see Tool live, you'll understand what riff mastery is all about. Flow, scat, flow.