With ringtones sales overtaking those of singles, record and phone companies are queuing up to capitalise on the trend, writes Oliver Burkeman

If you need someone to blame, blame Francisco Tárrega, the 19th-century Spanish musician considered by aficionados to be the father of the modern classical guitar. Most of what we know about Tárrega's life tends to inspire sympathy: he suffered from ophthalmia, a particularly nasty form of conjunctivitis, and was said to have contracted it as a child when he was nearly drowned in a poisoned river by a mentally disturbed nursemaid.

But feelings of pity soon give way to fury when Mark Squires, head of communications in Britain for the Finnish mobile phone company Nokia, plays you an audio file of Tárrega's masterpiece Gran Vals. A few bars of a wistful melody and then, suddenly, there it is: the 13-note phrase that feels like it's been hardwired into your brain since birth, or at least the early 1990s, and which has become universally known - even, sadly, among classical-guitar lovers - as that really annoying Nokia ringtone.

"Annoying? Oh, it's no more annoying than 'ring ring! ring ring!'," Squires says heartily. "I think it's a little bit more gentle on the ear, actually." Still, he admits, when he hears it ringing on live TV broadcasts, "you do think, 'silent button! silent button!'."

Looked at from one angle, then, the astonishing news that sales of ringtones downloaded to mobile phones are expected to overtake sales of CD singles this year is good news: at least there will be more variety. About €55 million worth of ringtones were sold in the UK last year, according to the trade group Mobile Data Association, largely by mobile-phone users paying between £1.50 and £3.50 a time to have tunes sent to their handsets using text-messaging technology. By the end of this year, they claim, this nascent industry is set to record an income of €100 million, nudging past singles sales, which the record industry forecasts will bring in only €95 million.

Increasingly, as with Sugababes' recent single Round Round, record companies targeting younger demographic groups find themselves marketing the ringtone version of a song as energetically as the CD itself, either making it available with a code purchased with the disc or scooping up a generous percentage in royalties every time it is bought from a third party. With many handsets now capable of playing polyphonic sound, the consecutive single beeps of Tárrega have been replaced with something more akin to a moderately advanced electric keyboard, plus percussion.

The first manufacturers of the telephone, notes the technological historian Jon Agar, didn't seem to foresee that it might be used for two-way communication (as opposed to sending one-way voice messages). Mobile-phone companies, similarly, were taken aback by the explosion in text messaging in Europe and Japan and remain broadly baffled by its failure to explode in the US, where walkie-talkie functions linking pairs of cellphones are still much more popular.

For Agar, that ringtones have become such a fad in the playground and at the watercooler - and a constantly updated tune, among some teenagers, the new currency of cool - shows, once again, how it is the users of technology who call the shots. "Like fashion in clothes, it's another way of expressing individuality, and this time, expressing it to anyone within earshot," he points out. "In that sense it communicates better than fashionable clothes, which might take a trained eye to spot."

Look closely at the hyperbolic yet exceedingly vague advertising campaigns for the much-heralded new generation of 3G phones, Agar notes, and a similar confusion is evident. "It's clear that the companies themselves don't have a very good idea what they'll be used for. They've spotted this pattern in the past" - that if you bundle in enough features, one of them will snowball into a craze - "and they're hoping that it will repeat itself. Not least because it shores up a lot of their marketing decisions if it does."

Already, according to some mobile- phone retailers, a handset's capacity for picture-messaging - its ability to beam detailed, full-colour illustrations from one user to another - is replacing the question of how many tunes it can store as the key question for younger consumers. But not, one suspects, before a plethora of web-based ringtones firms have cashed in on the phenomenon, among them the South African company iTouch. "We produce and sell the ringtones, we collect the money, and we pay the royalties," explains iTouch's Matt Hardwick. Take Justin Timberlake's recent single Rock Your Body: the firm did a deal with Zomba, his record label, and so now, "if you purchase the single at HMV or Virgin, inside it there's a sleeve which contains mobile services based around Justin Timberlake: a logo [for your mobile phone\] and a ringtone, both monotone and polyphonic". This, Hardwick explains, is "an opportunity to broaden your brand experience".

"At the moment I'm rotating between Wayne Wonder, Shaggy and a few others," says Claire Morton (15), a bona fide member of the ringtone demographic and part of an entirely unscientific survey conducted on the streets of north London. "I always swap ringtones with friends, and I've bought about three CDs so I can download the ringtones that come with them." "I call up the numbers in the back of magazines," says Kerry Armitt (18). "They say it will cost £2, but when I rang up £9 of credit came off my mobile phone."

But most insist they can find most ringtones for free. "I've just got a new phone from O2 and they give you two free ringtones," says Jack Wright (16). "After that I won't pay for them. I'll get them from the Internet."

And it is this, perhaps, that will ring the loudest alarms in the corridors of iTouch and its rivals. The record industry is eyeing mobile phones not just as a source of extra revenue but, possibly, as a delivery system for digital music, jumping belatedly on the Internet music bandwagon it missed so spectacularly the first time around.

The billing relationship that mobile phone users already have with their networks - the system through which they also pay for ringtones now - offers an extraordinary second chance: a ready-made way of charging for music track by track. Indeed, if Nokia's Squires has his way, users wouldn't even pay once to own a downloaded track for ever - they would pay a smaller amount whenever they wanted to listen to it.

None of this, however, is going to fly if the technology's real users - as usual, the most innovative minds involved - can find enough ways of transferring music from free Internet sources to the phones in their pockets.

"I remember it quite clearly," Squires says. "The first Nokia phone with \ ringtones came out and everybody within the company suddenly wanted it. We began to think: there's something in this . . . . Later, a Finnish student who worked for us during his holidays designed a ringtone composer [for the Nokia 9000\] - you could type music in on a musical stave." The company developed a system for sending the ringtones to and from the phone, and in 2001 they made the relevant software code open for all. And then, recalls Squires: "There was an explosion."

In a study of mobile-phone use commissioned by Motorola, the academic Sadie Plant wrote: "The warbles, beeps and tunes of the mobile have become so common that their calls have begun to constitute a new kind of electronic birdsong, changing the soundtrack of the cities and altering the background noise in regions as varied as the forests of Finland and the deserts of Dubai.

"Many urban songbirds have become adept at impersonating mobile tones and melodies . . . . Like a calling bird, a ringing phone demands a response. Public uses of the mobile spread this tension to all those within earshot, while leaving them powerless to intervene: only the person to whom the call is made is in a position to respond."

She was writing before the proliferation ofpolyphonic tones, let alone the surge in downloading; there does not yet appear to be any ornithological account of how urban birds are responding to the increased variety and complexity of ringtones, although it seems likely that they will be up to the challenge. This is the price we pay for modernity: starlings singing Justin Timberlake.