Glasgow guitar warriors Mogwai have been cultivating a reputation for genius since forming six years ago and their brilliant new album 'Rock Action' is the finest harvest yet.

Flats of the Sacred. Watch Out You Slut. The Exorcist III. Warning: Unattended Children Will Be Set On Fire. No, this isn't a shameful list of banned video nasties, but some of the working titles for the latest Mogwai album. In the end, they settled for calling it 'Rock Action', about as accurate a description of Mogwai as you'll find, although they're a little bit more reserved than they used to be.

Mogwai seem to live in a world all their own. There's Stuart Braithwaite, aka pLasmatron (guitar and, when the feeling takes him, vocals), John Cumming, aka meat (guitar), Dominic Aitchison, aka Dominic Christ (bass), Barry Burns, aka St Francis of Assassin (keyboards) and Martin Bulloch, aka bionic (drums).

They're not your normal band, Mogwai. More like a gang, really, violently storming the barricades of musical mediocrity with a fierce combination of reckless hedonism, terrifyingly loud gigs and the odd bit of provocation (they once made an EP in protest at Lanarkshire council's curfew for teenagers, entided 'No Education=No Future (F*** the Curfew)', and at T in the Park two years ago caused a bit of a rumpus with their "Blur: are shite" T-shirts).

Back when they formed, in Glasgow six years ago, Mogwai songs - if you could call these sprawling, feedback-drenched epics 'songs' - were one of two things: loud, or louder. There were occasional quiet parts, granted, but they seemed to be there for the band to take a breather.

However, no matter how loud, no matter how distorted and no matter how brutal Mogwai songs became, they somehow stayed beautiful. With 'Rock Action' they've refined their core values; there's still noise, but it's more careful, measured, calculated, and only occasionally does it layer itself on top of some of the most gorgeous music that you'll ever hear. Guitars shimmer and loom, strings cascade, electronic boxes click and stutter and whirr, vocals slide in and out of earshot every now and again.

Braithwaite (and the rest of the band) are in Dublin, following an explosive gig on Bute the previous weekend, where 500 revellers went on a day trip to Rothesay to see the band perform at the seafront Pavilion, and he is explaining the relatively concise nature of 'Rock Action', a single album compared to the previous two doubles.

"We wanted to make this album under 45 minutes," he says, adding that "it was good to be able to choose the ones we felt had to be on there."

So, nothing to do with all those prog rock accusations that have been levelled at them? Not a bit, insists Braithwaite.

"We're just trying not to be boring. I think if you played any prog rockers our tunes, they'd be quite horrified at the simplicity of them, to be honest."

The prog rock accusations, he says, were to do with the length of the tunes (and there are plenty Mogwai tracks that clock in above the eight-minute mark).

"Well," he confesses, "there's that and the fact that we all wear wizard outfits on stage these days. And we thought if we give people a much shorter alb~ they won't notice our forthcoming lO-part adaptation of Lord of the Rings."

That's coming next, apparently. "Yeah, it's being unveiled as we speak. We had to come to Dublin because we needed to get some leprechauns," he snorts.

"We didn't even ask them," he continues, "we just grabbed them off the street and bundled them into the back of a van, and ripped their tongues out. We're going to chuck them onstage and get them to entertain the masses."

Quite. So, Stuart, the new album...

"We'd done quite a few shows with the Super Furry Animals, and we were quite good friends with them," says Braithwaite, explaining how they coaxed the Super Furrie's vocalist, Gruff Rhys, into providing vocals for the spectral, string-drenched 'Dial: Revenge'. "We didn't think it would suit anyone in the band to sing it and we wanted something a bit more soaring."

Rhys's vocals certainly do that, his lilting semi-falsetto all the more eerie for being in Welsh, Rhys's native tongue. The words, apparently, are "about how in Wales, the public phones say 'dial', like they do everywhere. But 'dial' in Welsh means 'revenge"'.

So it's that, says Braithwaite, "Plus other abstract concepts that only make sense in his mind, all this stuff about frankincense and myrrh and so on."

It's one of the few tracks on the album with vocals, but don't let yourself be fooled into thinking that as a mostly instrumental album, 'Rock Action' is a very cold, emotionless fish.

By turns warming, playful, lush, deafening, and distorted, it's the closest Mogwai have come yet to condensing the power of their live shows on to one record. There's no excess, no flab on this album; in the eerie grinding of tracks like 'Sine Wave' and the epic, fractured beauty of '2 Rights Make 1 Wrong' there's all the beguiling wonder and locked-groove hypnotism you could want.

Despite 'Rock Action' being their third album, however, and despite the critical reverence and the years of gigging, Braithwaite insists that he still feels young.

"Am I a veteran?" he muses. "Not particularly, though it's six years now, and that's really the equivalent of - when we started the band - bands who started in 1989. So that is vaguely scary, but I don't feel like a veteran. An incompetent veteran, perhaps."

Mogwai's success is all the more impressive given that they are mosdy an instrumental band who take great pleasure in stretching out most of their songs to a hypnotic, interminable length (their encore at the Bute gig, a Jewish prayer called 'My Father; My King', lasted for a mesmerising 20 minutes, and went all the way from distant, quiet strumming to gorgeously apocalyptic, furious noise, encompassing the five band members and a brass section).

But Braithwaite claims that, for the band, it has very much been a pretty gradual experience.

"It's not like waking up one day and finding out that everyone thinks that thee sun shines out your arse," he notes.

So have Mogwai been able to keep a real sense of perspective about their success thus far?

"Ah," Braithwaite says with a slight laugh, "we've always really known that the sun shone out our arse."