The Cardiff Barfly may exude many things - including a regrettable and all-pervading aroma that can be traced back to the gentlemen's lavatories - but a sense of glamour is not among them. Outside, photocopied posters advertise forthcoming musical attractions. The gig-goers of Glamorgan are invited to enjoy an appearance by the unpromisingly named Annotations of an Autopsy, an evening of extreme metal featuring not just Hate Eternal, but Cephalic Carnage as well, and the 2008 tour by veteran punks the UK Subs, complete with lead singer Charlie Harper, now 64 and still dutifully belting out Stranglehold and CID for anyone tough enough to brave the smell of the gents.

Inside, the members of Alphabeat sit huddled in what may be Britain's least salubrious dressing room. Handily located so that the band have to leave via the Barfly's front door and walk down the street to reach the stage, it offers an intriguing line both in refreshments for the band - chief among them a tub of hummus that would cause lesser mortals to call health and safety and cancel tonight's show on the spot - and graffiti. A wag with a permanent marker has covered the wall in band names doctored to reflect a scatological bent. "The White Shites," reads vocalist Anders SG. "U Poo. Limp Big Shit."

His bandmates chuckle, but there's something deeply incongruous about finding Alphabeat in these surroundings. For one thing, they have a platinum album, albeit back home in Denmark. For another, ever since they formed at school in the small town of Silkeborg, the sextet have unabashedly dealt in feelgood chart-friendly pop. As if to reiterate the fact, their forthcoming album, This Is Alphabeat, features a gleeful assault on the eponymous 1978 debut single by John Lydon's Public Image Limited. The original is the kind of record that serious rock fans discuss in hushed and reverential tones. Alphabeat's version replaces Keith Levine's scything post-punk guitar riff with jaunty whistling.

"I think we did it because we know that we are very pop ," says guitarist Anders B. "So we thought it was quite a funny way to turn the song around because it was obviously a song that came just after punk" - he pronounces it "poonk" - "and we thought in a way, in this big indie scene that's been here for quite a long time now, we were outsiders with this pop music." He frowns. "We don't want to go as far as saying we feel as poonk as Johnny Rotten," he adds, hurriedly. "I don't know what those guys would think of that."

There's an argument that suggests one of the main reasons you might consider dealing in feelgood chart-friendly pop is to avoid having to sit in the dressing room of a grimy rock venue like the Cardiff Barfly. After all, pop is supposed to be the genre that fast-tracks its stars into a glittering world of TV appearances, expensive videos and product endorsement. Pop stars don't pay their dues on what's known as the toilet circuit. If they perform live at all, they tend to do so in the kind of venues where Annotations of an Autopsy and the UK Subs are unlikely to ever tread: arenas packed with screaming, glowstick-waving kids. Nevertheless, Alphabeat seem strangely at home here, amid the graffiti and the lethal-looking dips and the posters for the forthcoming show by Canadian hardcore poonks the Cancer Bats.

That may be because they've been here before. Last year, with their sights set on wider success, they relocated from Copenhagen to London, and began doggedly touring the lower reaches of Britain's live circuit. "We've played shitty venues for two or three years now," says Anders B. "I think it works. It definitely takes some of the pop-star thing out of it, but we're quite happy about that actually. We played some concerts in Denmark on a huge stage, where we just didn't feel like we had that much to offer. We felt like we were lying to people. Now, we're just enjoying the small venues."

In any case, small venues are very much the point of their current tour. Dubbed the Wonky Pop Tour, it's been heralded in some quarters as a coming-out party for a new kind of pop star, here to save the genre from being finally, fatally smothered by Simon Cowell's army of anodyne talent-show winners, and to rescue the charts from the preponderance of "landfill indie" bands that currently provide the meat and potatoes of the daytime Radio 1 playlist.

The Wonky Pop artists are unmanufactured but unashamedly melodic and capable of playing live without recourse to lashings of dry ice, troupes of dancers and an interlude during which they fly around the stage on wires. As well as Alphabeat, it features the vaguely psychedelic pop-soul of Leon Jean-Marie, a dreadlock-sporting refugee from a Damage-style boyband who once toured with Steps, and Vincent Frank, a wiry 23-year-old who plies an intense brand of self-produced electro-pop under the name Frankmusic.

All three hark back to an 80s they're too young to remember, not just because of specific references in their music - Alphabeat's sound is not unlike a Dayglo take on Let's Dance-era Bowie, Leon Jean-Marie is audibly in love with Prince, Frankmusic vaguely resembles Soft Cell had they been produced by Daft Punk - but because they seem to embody the kind of pop star that held sway in the era before Stock, Aitken and Waterman's legion of interchangeable poppets took over the charts.

"In the early 80s, the idea of a pop star was someone who was unusual or eccentric or fantastic in some way," says Peter Robinson, of website popjustice.com, one of the tour's sponsors. "Everything that's happened in the past 10 years, especially with TV shows where people are voted out if they're a bit weird, suggests the best way to become a pop star is to keep your head down and not get noticed, not have much of a sense of individuality or style."

He baulks at the suggestion that hawking around venues like the Cardiff Barfly is somehow at odds with the notion of being a pop act. "This kind of grassroots approach to pop isn't something which can apply to all types of pop - the new Britney, or the new Girls Aloud, would need to appear with a bang - but the idea that pop music requires an impenetrable fourth wall in order to be pop isn't very helpful. Pop personas are about projecting the idea that you're a star whether you're headlining at the O2 or third on the bill at a shithole like the Leeds Cockpit."

Nevertheless, Alphabeat's manager Ian Watt claims the idea for the tour was conceived amid considerable trepidation: "It could have fallen flat on it's arse. Hand on my heart, I really couldn't have told you what kind of people were going to be in the audience."

By the time it reaches Cardiff, however, the mood around the Wonky Pop Tour is bullish: the venues have been packed, all three artists appear to be on the up. Alphabeat's second British single, Fascination, recently spent four weeks in the Top 10. Leon Jean-Marie is, as he puts it, "getting a lot of love from Radio 2" for his debut Bed of Nails. If his forthcoming album fails, it certainly won't be for want of blue-chip collaborators, who include Mark Ronson, Cathy Dennis and Swedish production duo Bloodshy and Avant.

And then there is Vincent Frank, who, in a pub around the corner from the Barfly, lays out a detailed plan for world domination that involves simultaneously signing a major label deal and starting his own record label, collaborating with Madonna's erstwhile producer Stuart Price, "a really stinking, completely epic and mental live show", and ends somewhere in Hollywood with him pursuing a career in acting and scoring films. Keen to point out that the first three have all been ticked off, leaving only Hollywood on his to-do list, Frank is enormously engaging, uproariously funny and faintly terrifying. It's hard not to feel that if he doesn't become a pop star, it'll be pop music's loss.

Meanwhile, Watt, who also manages Mika, has cannily copyrighted the name Wonky Pop and is planning to extend the brand in a manner that would win the approval of Simon Fuller: he's preparing two further tours, a club night and a series of one-off dates in London. Whether this makes the whole enterprise seem a little less organic, unmanufactured and indeed wonky than it's perhaps making itself out to be is a moot point, but there are no shortage of artists who want to get involved. "There are at least 20 bands that fit loosely into this genre," says Watt. "I'm hoping it will be a self-fulfilling thing, that people who go to the gigs will want to go out and create their own version of it."

"I think there's definitely something happening," says Robinson, who 18 months ago appeared in the Guardian's pages suggesting major labels should "put their money in a field and set fire to it" rather than spend it trying to launch a new pop act. Recent events, however, have caused him to change his mind: "People aren't just buying pop music, they're buying music from artists who aren't necessarily English-speaking or from the UK: Robyn, Alphabeat, September. There was always this perception that Eurovision was some kind of definition of what European pop music was like, and people were able to put it in a box and dismiss it. I think the fact that it's being playlisted at Radio 1 has made a difference. I'm optimistic about what's coming up for the first time in ages. There's lots of stuff knocking about which is really exciting."

Quite what has caused the putative shift is a matter of some debate. One theory suggests that Alphabeat et al simply have a wider reach than their manufactured forebears: "It's pop music being made by adults for their own peer group, totally at odds with the era when pop music was made for and marketed at children," says Robinson. Another is that the teenagers who bought tickets to the Wonky Pop tour were once seven-year-olds whose musical flashpoint was provided by Busted and Avril Lavigne. They moved on to indie and emo, but have tired of the glut of Identikit indie-rock bands and have come back to what they know: pop artists who write their own songs and play their own instruments.

Another suggests that indie music has now become so mainstream and so craven in its pursuit of success that listening to pop represents a way of setting yourself apart from the herd: "Pop got to the point where the music wasn't the most important thing about it, where the songs were no good," says Robinson. "I think what's happening now, with Scouting for Girls, the whole flipchart indie thing, is going to do the same for guitar music. Pop music has become a bit of an alternative."

Whatever the reason, in the Cardiff Barfly at least, it appears to be working. The crowd - late teens and early 20s, dressed up, with a definite female skew - seem happy to support Frankmusic's ongoing plan for world domination. "Pop music was seen as a dirty thing," he reflects later, "but porn is seen as a dirty thing, and that doesn't stop people from liking it." Leon Jean-Marie exits the stage to be surrounded by a crowd of eager girls: if he isn't quite being mobbed, it's not far off. Alphabeat are a triumph: the audience reaction to Fascination virtually drowns out the band. By the time all three artists come on stage for an encore of Daft Punk's Digital Love, a happy and infectious pandemonium reigns. No one seems bothered by the smell of the gents at all.

· The Wonky Pop Tour is at the Forum, Tunbridge Wells, tonight, then Night & Day, Manchester, tomorrow. This Is Alphabeat is released on Charisma on June 2. Leon Jean Marie's album Bent Out of Shape is released on Universal on June 30