The internet phenomenon: modern zeitgeist - or a cynical PR ploy?

It could well be the fastest example of "build 'em up, knock 'em down" since Scrapheap Challenge. The Scottish singer-songwriter Sandi Thom had been touted as the darling of the online music scene for her daring basement gigs. The story was that, fed up with touring, she set herself up in her south-London home and broadcast sets on the internet. She built up such a large following that she ended up being signed by the major label RCA, part of the Sony BMG group.

But with her debut single, "I Wish I Was a Punk Rocker", set to reach No 1 this weekend, suspicions have been raised about her rise to fame. If she was so strapped for cash, how could she afford the bandwidth (the internet broadcasting power) to support tens of thousands of viewers? And what role did her publishing company and PR agency play?

While bloggers have cried foul, the basement gigs were Thom's own idea, her manager maintains. He says all he and the artist's PR company, Quite Great, did was ensure word got out via e-mails and articles in the national press.

But is the music industry finally getting to grips with the internet and using it to hype artists? Suspicion already rests on the sudden success of Arctic Monkeys, the Sheffield band whose debut, the fasting-selling album ever, was a dramatic display of the effect of word of mouth, much of it online. Some commentators have wondered whether their apparently spontaneous success has, in fact, been manufactured. The band recruited a PR company to look after their interests even before they were signed. Anton Brookes of Bad Moon was the man lucky enough to pick up their scent early on. "Their manager sent me some demos, so I went to some early shows and thought they were really good," he says.

Their online presence, he says, came about only by accident. Although it has been long assumed they used the blog network MySpace to break themselves, the Arctic Monkeys' much-mentioned site there was in fact set up by a fan, and the band or their backers had little to do with the dissemination of their music online, Brookes says.

"People think the band did it, but that's just not the case. It was all generated by enthusiastic fans. A few years ago, it would have involved fanzines and cassettes. New technology means it just happens a lot quicker," he says.

Nor is it uncommon for artists to work with press officers before they gain a contract. PR companies are happy to work for free with groups they have high hopes for, as it allows them to create ties before a band is signed to a label and encouraged to work with its in-house marketing team. In the past, Bad Moon has got in early with Kaiser Chiefs, Ash and even Nirvana, when they were heard in the UK only by John Peel's listeners. Although no band has enjoyed such instant acclaim as the Arctic Monkeys, Brookes sees PR involvement as part of a typical career development.

"It can be key to getting a young band signed," he says. "Some labels won't be interested in an artist until they've been in the NME or another publication, but when that happens they all turn up to gigs. Everyone watches everyone else."

The latest artist to be connected to the internet is Lily Allen, daughter of the actor Keith Allen, notorious for her own MySpace site to which she contributes demos and her opinionated blog. Again, though, an online presence was important in spreading the word before the limited release of her debut single, "LDN".

Her press officer at Parlophone, Murray Chalmers, denies that her label has sought to capitalise on this. "MySpace has been a contributing factor to her success, but she was signed quite conventionally at the end of last December on the strength of her music alone. About the same time, she started putting her music up, but we had nothing to do with it." Chalmers says word of mouth works only when the music is strong in itself. He says people find out about Lily through her website, but just as many are drawn there by hearing the music on Radio 1, where Jo Whiley made her first full release, "Smile", out next month, single of the week.

No artist is above a bit of hype. Colonel Parker played up Elvis Presley's sexy performances to gain him notoriety. Likewise, Malcolm McLaren was instrumental in getting The Sex Pistols known beyond the pub circuit, through their combative live performances and raw sound. However, not all notoriety can be managed. Frankie Goes to Hollywood might not have got to No 1 if the DJ Mike Read had not encouraged Radio 1 to ban "Relax" from its playlist - but who was to know he would get so het up?

Lily Allen may be the new queen of MySpace, and the Arctic Monkeys should thank their fans their commitment, but both artists have something to offer beyond the hype. Allen's brand of pop contains a wry wit, while the Monkeys offer a distinctive lyrical voice. We are still waiting for a genuine monster to be spawned online, in the manner of the Crazy Frog ringtones or the one-hit wonders Babylon Zoo, who came to fame via a 30-second snippet on a jeans advert.

Perhaps it will be a long vigil. Blogs, downloads and sites that allow thousands of bored office workers to upload video footage - with so much media to play with, it is difficult to engineer hype in the manner of the great charlatans of old, since it relies on so many people to join in the fun.

Managers, press officers and labels can use the internet to promote their artists, but if the product lacks quality or novelty value (thank you, Nizlopi), then few people will be convinced enough to add their support.