The nine mask-clad monsters of Slipknot take their dense, hectoring sound from some impeccable sources: Black Flag, Public Enemy, Slayer, Ministry, Rage Against the Machine. Unfortunately, the Des Moines band's sensibility more often suggests professional wrestling, slasher movies and the Insane Clown Posse. The group's self-titled second album (after a homemade 1996 disc sweetly titled "Mate, Feed, Kill, Repeat") is sonically visceral and thematically inert.

To either celebrate or deplore depersonalization--like, whatever, right?--Slipknot's members go by numbers, although their given names are not closely guarded secrets. (Singer No. 8, who wears the mask of "Texas Chainsaw Massacre" fiend Leatherface, is actually named Corey Taylor.) The musicians claim the uncomfortable masks make them more intense on stage, but the band's intensity doesn't really need boosting. Whether purveying their rancor as the metallic funk of "Spit It Out," the metallic drum'n'bass of "(Sic)" or the metallic hardcore-punk of "Eyeless," Slipknot is impeccably belligerent. Still, the nine blitz-rockers' imprecations are so generic and secondhand that you might wonder if what really makes them mad is the fact that they don't have anything much to be mad about.

With pummeling guitars and song titles like "Suck" and "Choke," Kittie's "Spit" can rival "Slipknot" for pugnacity. The band's gimmick, however, is more innate than wearing masks: All four members of this Canadian metal-punk band are women, which is still a novel (though certainly not unique) lineup for a headbanging ensemble. Too bad that's virtually the quartet's only distinguishing feature. "Do You Think I'm a Whore?" asks singer-guitarist Morgan Lander in one of the band's confrontational songs, but that's not the pertinent question. The real concern is that, after four or five of these pounding rockers, Kittie becomes a bore.

Both appearing Sunday at the 9:30 Club with Will Haven.

* To hear a free Sound Bite from Slipknot, call Post-Haste at 202/334-9000 and press 8104. For a Sound Bite from Kittie, press 8105. (Prince William residents, call 690-4110.)