Some things you won't find on a Mogwai record: lyrics, verses and choruses. What you will find: some of the most exciting music being made today.

Mogwai are loud. Really loud. Permanent-hearing-damage loud. "I think people in the audience should wear earplugs," warns guitarist Stuart Braithwaite. "The point of the volume is to feel your body being shaken. Hurting people's ears isn't very nice - if they put some toilet paper in their ears, that would help." The loudest show Braithwaite ever saw himself was My Bloody Valentine in 1991, in his hometown of Glasgow. He remembers that his pants flapped, vibrating from the sonic waves. "This year, someone told me that they had seen their trousers flap at one of our shows," he says. "I felt all proud."

Things not commonly found on Mogwai records: verses, choruses or lyrics. When there are words, they tend to be buried in the mix - the vocals are just another instrument. Much of Mogwai's music is abstract, experimenting with tones and texture and contrast. Rock Action, their third proper record (they've also released two compilations), begins with "Sine Wave." One synth drones; another slowly plucks out a melody. Percussion fades in - so distorted that you think your speakers have blown their tweeters. Guitars fill out the ambient sound, growing ever louder; and then, after four minutes, it all washes away. It's played on rock instruments, but it owes more to twentieth-century composers such as Steve Reich and Arnold Schoenberg than it does to Chuck Berry. And it's some of the most exciting music being made today.

Mogwai consider themselves a rock band: The one time they played for a seated concert audience, it quite disturbed them. Their love of rock & roll sweat is so great that when they enter a dressing room occupied a week earlier by Iggy Pop, they sniff the couch for any residue of his Iggish aroma. The band consists of five young Scottish men, ages twenty-three to twenty-seven, with brogues so thick that most Americans understand only half of what they say. The five-foot-five Braithwaite is Mogwai's frontman, if not their leader; he enjoys talking to the crowd, doing interviews and winning arguments. Drummer Martin Bulloch is the group's best cook, a veteran of a Glaswegian Chinese restaurant. Bassist Dominic Aitchison is the group's video-game king. Guitarist John Cummings is its theorist, prone to writing essays on the nature of sound. And utility infielder Barry Burns serves as comic relief. Confronted with a wide array of American sweeteners for his tea, he declaims, "You've seen Rambo. You've seen Predator. Now - Sugar in the Raw."

During a monthlong tour of the United States, Mogwai have a day off in Chicago. They eat lunch at Wishbone, a soul-food restaurant across the street from Oprah Winfrey's studio. "I hate Oprah Winfrey," Aitchison says.

Why? "You ask us that like our hatred is rational," Braithwaite says. At lunch, the band members gently insult one another and compare recent purchases: Braithwaite has bought an Empire Strikes Back T-shirt, Bulloch a gatefold vinyl copy of the Clockwork Orange soundtrack, Aitchison an Iron Maiden lunchbox.

"I paid ninety-three dollars for my trainers," Burns says of his sneakers.

"I paid the square root of fuck-all for mine," Braithwaite replies.

Burns tastes some of the hot sauce and says, "I think it was made of children. Spicy children."

Mogwai have an upscale tour bus, even though their record sales are better suited to a van. "If we were in a van, we'd play shite," Braithwaite says. "And when you come back to a town where you played shite, people remember." Mogwai cheerfully concede that hit singles and platinum records are not in their future. So they make less money than they would with steady jobs - but get to play their music all over the world and ride in a bus with a DVD player and a satellite dish.

"I prefer food to breathing," Burns says. "I could eat for Scotland in the Olympics. But my problem is, I'm thinking about the next bite before I've even got this one in my mouth." Braithwaite's cup of tea is accompanied by a wedge of lemon. "Does anyone remember me asking for milk with my tea?" he demands. "The same thing happened yesterday. They're out to get me, as Axl Rose first sang." Mogwai have covered "Don't Cry" and sometimes talk of plans for an entire EP of Guns n' Roses covers, a project unlikely to ever come to fruition. The conversation turns to drugs and whether the band should procure some Ecstasy. "I'm glad Ecstasy's invading America," Braithwaite says. "It'll make the music better - you wouldn't want to take it and listen to Creed." With a journalist sitting at the table, Braithwaite is trying very hard not to dis other bands, but sometimes he can't help himself. It's not malicious - just habit. Mogwai got some of their first headlines for printing up T-shirts that read blur are shite. On that band, at least, Braithwaite is unrepentant: "They're a commodity. I don't think anyone in Blur would buy their own records."

Mogwai started because the members were tired of playing bad covers of Funkadelic and "Brown Sugar"; they wanted to make music in the tradition of Joy Division and the Jesus and Mary Chain, to make records they would want to buy. Braithwaite and Aitchison, both college students in Glasgow, met at a Ned's Atomic Dustbin concert and formed Mogwai in the summer of 1995. (The name comes from the film Gremlins, inaugurating a Mogwai habit of grabbing album and song titles at the last minute from whatever seems convenient: National Enquirer headlines, telephone booths, drunken ravings of band members.) They recruited Bulloch and Cummings and by the fall were playing shows and releasing singles. "At early rehearsals," recalls Braithwaite, "we'd play the song for two minutes and then just make this incredible noise. That took over for a long time." They realized they didn't need the pretext of a traditional song to make organized noise.

Mogwai's 1997 debut, Young Team, received rapturous reviews, the norm for Mogwai's career; now they seem to enjoy the pans more than the raves. In 1999, they recorded the sixty-seven-minute Come On Die Young in three weeks, recruiting Burns to fill out some tracks on flute. Although he has music-conservatory training, he was asked to join Mogwai because he made them laugh. Lately, he's been playing more keyboards and guitar - Aitchison worries about the Jethro Tull implications of the flute.

Mogwai started writing quiet sections of songs to accentuate the high volume of other sections. Then they started focusing on those still, subdued passages. Since they can't force you to turn up your stereo full-blast at home, they find other ways to experiment with sonic texture. For Rock Action, they had three months in the studio - ample time to experiment with string sections, vocals and high-tech gadgets. "Whenever we don't know what to do with a song, we just put it through a digital delay," says Aitchison.

Mogwai are not the only rock band experimenting with sonic textures in this fashion. There are enough like-minded folk - Tortoise, Godspeed You Black Emperor! and recent Radiohead - that the genre has been given a label: post-rock, a term Mogwai reject with the stock reply that "post-rock" means having a beer after the gig. Some critics have said that post-rock is just a new term for prog-rock; asked what the difference is between Mogwai and prog-rock, Braithwaite grins and replies, "Capes."

On a Tuesday evening, Mogwai find themselves in Detroit's Majestic Theater, which is more mildewed than majestic these days. There's a tub of beer backstage, which they drink moderately; they used to get so inebriated before shows, they could barely play. Groupies are nowhere in sight. Even if they were, the band would have no interest: They all have steady girlfriends back home. Braithwaite's sweetheart is a promoter; they met when she brought ice into the dressing room. "Say 'please' and 'thank you,' and you end up with a wife," he observes. They're getting married this summer.

Braithwaite types away on a laptop, answering e-mails from fans. "How many l's in tolerance?" he asks. "It's not a word I spell too often." Replying to a German correspondent defending Blur, he types FUCK OFF. Bulloch enters, sporting a mohawk and a hospital ID bracelet. The previous evening, he visited the emergency room after his pacemaker shifted under his skin (he has a hole in his heart - a non-life-threatening condition). They write a set list on the back of a styrofoam plate. They've downloaded the list from their last time through town to ensure they don't repeat too many songs. Whenever there's disagreement over whether they should play a song, they quickly vote with a show of hands. Mogwai are that rarest of rock bands: a democracy.

Burns warms up on the flute by playing Status Quo's 1968 hit "Pictures of Matchstick Men," and then the band ambles onstage to a prearranged setup of twenty-nine effects pedals and boxes. On record, Mogwai's tracks can sound compelling but improvised, as if they were cobbled together in the studio. Live, the band demonstrates the precision of its compositions, as songs turn from quiet to loud on a ten-pence coin. Songs that were subdued become overwhelmingly loud onstage, as if Mogwai are hammering down a thunderstorm into a shape they can work with. Melodies drift in and out, sometimes repeated behind walls of white noise. It's beautiful, and painful. The crowd stands still, hypnotized, all but the three people inexplicably dancing at the foot of the stage - members of opening band Bardo Pond boogieing down.

The encore is a hymn they like to call "The Jewish Song," taught to the band by famed hip-hop producer Arthur Baker. A chiming chord progression gets faster and louder - only to drop away and build back up, over and over, for twenty minutes. Braithwaite pulls up the hood of his parka in a futile effort to protect his eardrums. (He doesn't follow his own advice on earplugs.) Finally, the melody disappears underneath an ocean of distortion, as Mogwai spin random knobs on their instruments. They walk offstage, leaving the road crew to turn off the amps. When they finally do, everyone's ears are ringing and there's a loud silence, a silence filled with a threat that didn't exist before.