They're not jazz, they're not rock and they're definitely not post-rock. What they are is a new music craze. Ed Power meets The Jimmy Cake

The Jimmy Cake roll their eyes and pull faces when, confounded by their avant-garde fusion of jazz and pop, critics bandy about the "post-rock" tag, a lazy handle that is applied to self-consciously impenetrable music with a puritanical disdain for conventional songwriting strictures.

The nine-piece Dublin ensemble blanches at the suggestion that cathartic pocket symphonies such as Ignite The Doom Carriage and Elevenses represent arch exercises in obtuseness. Look a little closer, they plead. Sift through the tumultuous percussion, the cacophonous feedback blizzards, the screeching walls of brass and horn. Set aside all that is unfamiliar and alien and glory in the sleek, labyrinthine compositions glimmering within.

"Actually, I think our stuff is sometimes best appreciated in the background," booms Diarmuid Dermody, their leonine saxophonist and drummer. "When you're not consciously listening, it seeps in under your defences. You're responding to it at a very deep, very emotional level. "

They have certainly seeped into the affections of the capital's music press. Emerging from the ashes of Das Madman, a shambolic and short-lived drone outfit, the Jimmys have become a cause célèbre for local rock journalists. Last year's shuddering, swooning debut album, Brains, garnered ecstatic write-ups, with reviewers gushing over its innovative deployment of instruments such as accordion, saxophone, clarinet and xylophone.

A succession of triumphant concerts further buoyed the Jimmys' profile and gained them a wide local following, making Brains one of the fastest-selling independent releases of 2001. Tonight, the group stands poised to transcend its grimy indie-rock origins, when it unveils a commissioned 50-minute piece in Project art centre's Space Upstairs.

Amid the hyperbolic notices and glowing profiles, one question continues to nag. Why? Why did a set of friends raised in a city where experimental music is about as popular as bullfighting embark upon such an unhinged endeavour? Why not join a rock band? A jazz troupe? A nu-metal outfit?

"Personally, I'd be bored witless playing bass in a conventional group," harrumphs Simon O'Connor, the Jimmys' rhythm guitarist, who also plays glockenspiel when required. "To stand there, doing something that has been done a million times before? No thank you."

The group's distinctive marriage of chaos and melody - to these ears, at least, they come across as a mesmerising confluence of Belle and Sebastian, Neu and the American Analogue Set - emerged "by accident", says lead guitarist Vincent Dermody. The familiar parade of overly eulogised experimentalist totems - dishevelled noiseniks such as Sonic Youth, Throbbing Gristle and Spacemen 3 - don't feature prominently among the players' influences. Nor are they besotted jazz nuts. No Miles Davis freaks or John Coltrane proselytisers here.

"I don't think there are any elements in our music that you can isolate and say, there, that's influenced by jazz or rock or whatever. Our sound developed organically," he says. "It's a bit of a cliché, but The Jimmy Cake works like blotting paper.

"All the music we've ever listened to is absorbed and comes back out in a completely different way. We're sick of people lumping us with other musicians, because we believe nobody out there sounds anything like us."

Especially rankling are the unceasing comparisons to the Canadian label Kranky and Godspeed You, Black Emperor!, its 12-piece headline act, who are a maudlin collective specialising in anguished apocalyptic dirges. The tag plagues the Jimmys, manifesting with tiring regularity in interviews and reviews. It's got so bad that people have started coming to Jimmy gigs anticipating an evening of gothic existentialism.

Yet - and how they'll hate this - there are parallels. Like the Montreal miserabilists, The Jimmy Cakes boast nearly enough members to put out their own football team (Diarmuid Dermody jokingly refers to the band as a kibbutz). More relevantly, both acts encompass a dizzying parade of side projects. The Jimmys harbour a multitude of offshoots, running the gamut of cutting-edge genres - electronica, spasmodic jazz and crunching drone-rock among the most definable - and a tongue-twisting array of monikers: Thinker, Org, Front End Synthetics, Dead Plants, RSi and Chocochai 3k Battery. Some of them even find time to play in David Kitt's backing group. "Our side projects act as release valves," says O'Connor. "They give us space to express ourselves where, otherwise, we might be tempted to become indulgent within the Jimmy Cake."

Unlike Godspeed You, Black Emperor!, who are fiercely politicised, the Jimmy Cake don't regard mainstream success as a betrayal. Indeed, they show a rare business savvy. Recognising that our sluggish recording industry was unlikely to work itself into a lather over a project as uncompromising and unmarketable as Brains, the group financed and released the album on their own Pilatus label. Plans are already afoot for a follow-up - "the songs have been written, we just need to find the time to record them," says O'Connor.

Unencumbered by the pressure to deliver a radio-friendly product or justify themselves to a coterie of besuited taskmasters, the Jimmys sidestep the commercial headaches that have sunk so many Irish hopefuls.

"We all hold down day jobs and it really isn't such a trial balancing our nine-to-five lives with running a band. This is what makes life worthwhile," says Diarmuid Dermody.

Of more pressing concern are the constraints that the size of the group imposes on touring. A smattering of gigs in Cork, Belfast and Galway were gleefully received, and their public are baying for more. Unfortunately, it's unlikely we'll see a full-blown national tour any time soon. They've also turned down numerous requests to perform abroad.

"We're hoping to get to Britain sometime this year. It's a problem, though, with so many in the band. We may have to take a stripped-down version of The Jimmy Cake on the road," says Diarmuid Dermody.

As their profile soars and fan base proliferates, the Jimmys are, with characteristic wilfulness, laying plans for a radical overhaul of sound and image. It's important to keep moving forward, reinventing themselves at each turn, they say. Who knows what blissed-out melodies may yet emerge from their collective subconscious and creep into yours? Just don't call it post-rock.

•The Jimmy Cake play with The Acid Mothers Temple at Aunt Annie's, Belfast on March 29th and at Dolan's Warehouses, Limerick on the 31st, and with The High Llamas at Vicar Street, Dublin, on April 23rd and at the Savoy, Cork, on April 24th