"Three basic types of people come to see us play," O'Malley told me. "First, the people who are really into experimental music or metal — the passionate music lovers; then you've got the spectacle crowd, who come for the robes and the smoke machines; last, you have a group of people who are more interested in the physical aspect of it. Those are the people who are just like, I'm going to stand at the front of the stage for an hour and a half — can I take it? Will I wet my pants? Will I puke? I'm going to be at the very front, in front of these amps for 75 minutes, and then when it's done I'll feel liberated, or I'll feel like I've beaten the band or whatever, no matter how tortuous it is." I pointed out that it's fairly uncommon for a band to divide its fan base into the aural, the visual and the tactile: I'd expected him to make a distinction between metal and experimental-music fans. O'Malley nodded politely, then did his best to bring me up to date. "In the past three or four years, since the point when the Internet started becoming the primary source for discovering music, the lines between different styles have really begun to blur." He spread his arms as he said this, looking at me almost slyly, as if he were about to perform a magic trick. "There's so much access to so many different types of music now, it's no wonder that people aren't categorizing themselves so sharply. It's pretty awesome, really."

Southern Lord Recordings had no particular ideology or purpose at the beginning, other than to advance the cause of music that its founders made or liked — but there was no question, ultimately, what genre of music that would be. "I like heavy music," Anderson told me simply. "That's where I come from." When I asked O'Malley to explain the label's name, he looked down at his fingers with something verging on embarrassment. "You know that Slayer album from the 80's?" he mumbled. "'South of Heaven?"' I was beginning to understand. "I see," I said. "So, then, Southern Lord would be another name for—" "That's right," O'Malley said quickly, clearly grateful that I hadn't made him spell it out.

Over the last five years, Southern Lord has become something of an independent-music success story. As awareness of "drone metal" — as Sunn0)))'s take on doom metal has been labeled — and of other forms of unconventional heavy music has grown, both on purist metal Web sites and on college campuses, record sales for the label have risen exponentially. Eight years after its founding, Southern Lord has arguably become as closely associated with the experimental metal scene as Blue Note was with the hard bop movement of the 50's.

"They've got a good thing going with that label," says Ian Christe, author of "Sound of the Beast: The Complete Headbanging History of Heavy Metal." "It's become a known brand, the way that Sub Pop was in the early 90's — people will check out a record they've never heard of just because it's out on Southern Lord." The label's discography is diverse, as you might expect of Anderson and O'Malley: two Saint Vitus reissues; a much-acclaimed comeback album by the minimalist post-grunge band Earth (which once briefly featured Kurt Cobain on vocals); and a strangely beautiful suite of songs called "Triste," by the Australian experimentalist Oren Ambarchi, largely made up of single guitar notes played over gentle static. One band more than any other, however, has helped to put Southern Lord on the map: a well-mannered three-piece from Tokyo with the slightly improbable name Boris.

If Sunn0))) is the ZZ Top of experimental metal, with matching beards and Gibson Les Paul guitars, Boris might be the Kraftwerk, or the Ramones, or even the Jimi Hendrix Experience, depending on the album. The members of Boris, each of whom goes by only his or her given name — Wata on lead guitar and vocals, Atsuo on drums and Chinese gong and Takeshi on Cheap Trick-style, double-neck guitar and bass — approach heavy metal with the seriousness of theoretical physicists. Like Sunn0))), they have the requisite long hair and black tour T-shirts; unlike Sunn0))), they are clearly and undeniably a rock band, with identifiable song structures, singable lyrics and a charming and welcome willingness to pay tribute at the altar of Black Sabbath. The fact that Boris's lead guitarist is a graceful, soft-spoken woman who occasionally wears Victorian blouses onstage is unusual, certainly, but in no way outside the realm of your run-of-the-mill head banger's fantasy.

At first glance, therefore, you might wonder where the common ground with a band like Sunn0))) would lie. The answer, of course, is simple: Boris is omnivorous in its taste, obsessed with surprising its audience and, in the words of Greg Anderson, makes "beautifully ominous" music. Not only that, but the kids seem to like it. Boris is currently second only to Sunn0))) in total record sales for Southern Lord artists, and the band's new album, "Pink," has been winning ecstatic reviews from 20-something metal heads and middle-aged critics alike.

Image NOISE or noise? Boris, an art-metal band from Tokyo, plays both uppercase (Black Sabbath meets the Melvins) and lowercase (acoustic strums amid the din) versions. Credit... Miki Matsushima

Boris's success in America — which, though still fairly modest, is building up a remarkable head of steam — seems at once unlikely and inevitable. It seems unlikely not only because its members are relatively old (all of them are well past 30) and speak very little English but also because the band's identity shifts drastically from album to album: so much so, in fact, that a visual code has been developed for its record sleeves, the aesthetic equivalent of a parental advisory sticker. From CD's on which "Boris" is printed in uppercase letters (as in the case of "BORIS:Pink"), fans can expect Black Sabbath-by-way-of-the-Melvins heavy rock; if the CD in question features the band's name in lowercase lettering, they may need to check their expectations at the door. A recent lowercase Boris album, "Sun Baked Snow Cave," featured an hourlong collaboration with the Japanese experimental "noise" pioneer Merzbow, in which softly plucked acoustic guitar chords alternated with ear-piercing cascades of, well, noise.