That's not static on your radio, says John L Walters, that's Scanner's latest work
Voices, human ones, are the raw material of Robin Rimbaud's work. Disembodied voices that could be one half of a phone conversation or an interior monologue or the rambling speech of a person who is lonely or distressed. Under the nom de guerre of Scanner, Rimbaud quickly acquired notoriety by performing live with an electronic scanning device that intercepted mobile telephone calls, which he then manipulated and mixed with understated, throbbing synthesisers.

The result was entertaining and unsettling: the real-life pathos, violence or banality of the eavesdropped speech gave a dramatic edge to Rimbaud's ambling, ambient electronic improvisations.

More recently, Rimbaud has moved his attention to setting texts, and making pieces for radio or CD that use performers rather than "found speech". He is an incredibly prolific artist: recent work includes Accretions, a mildly scatological collaboration with performance artist Hilaire and (more interestingly) The garden is full of metal, a sequence of electronic tone-poems manipulating the recorded reminiscences of the late Derek Jarman. His latest opus is a "setting" of The Human Voice, an adaptation of La Voix humaine by Jean Cocteau, which will be broadcast tomorrow - Valentine's Day - as the last in Radio 3's current series of "radiogenic" commissions, Between the Ears.

Cocteau's La Voix humaine is the one-act monodrama from which French composer Francis Poulenc made his last opera in the late 1950s. The script consists of a virtually continuous one-sided telephone conversation, yet its genius lies in the way its flat, realistic phrases create the believable character of a young, vulnerable woman. The artless lines sound "found", just the sort of mobile-phone conversation that Rimbaud might have scanned while performing in Camden or Los Angeles. The woman's attempts to talk to her lover are even interrupted by various crossed lines.

A charade of communication is taking place, but the woman remains alone in her bedroom. If cyberspace - once defined by William Gibson as where you are when you are talking on the telephone - is lonely and frightening, so is this bedroom, with its unmade bed and harsh light as specified in Cocteau's original stage directions.

Poulenc expressed what he saw to be the "decadent" style of the woman's life by bathing the words in "great orchestral sensuality". Rimbaud makes no such judgement, and in that respect is closer to Cocteau's original. The solitary urbanite who communicates by electronics from a small, functional room could be a woman (or man) of the 1990s.

The Human Voice deals with some of the issues tackled by today's visual artists like Gillian Wearing. The musicologist Wilfrid Mellers once observed that Poulenc's version triumphs in "the genre now known as `performance art'", and Cocteau's preface stresses the importance of creating "a seated woman", framed by a proscenium arch, for his naturalistic portrait. It sounds like an old-fashioned painter's conceit: a woman, in a night-gown, in a bedchamber waiting for her lover, but the addition of the telephone makes it a work of the modern age.

Cocteau had an instinctive understanding of the heady cocktail of sex, death and technology years before Marshall McLuhan's "mechanical bride". Rimbaud treats Cocteau's monologue (minimally adapted by April de Angelis) with the techniques he uses for his live phone scans. At times the voice is echoed and repeated: the different treatments change the apparent location of the voice in (cyber)space and create a "layered" effect when they are edited tightly or overlapping. There is no conventional harmony or melody. In fact, when Rimbaud attempts something like a piece of conventional music, his palette of synthesiser and drum machine sounds is surprisingly conventional - as predictable as an old Pink Floyd record.

The most striking and original aspect of his technique is the disturbing use of noise - the digital detritus that comes from interrupted phone calls and badly tuned radios. There's a parallel here with visual artists who use the scraps and splatters of their studios to express a personal language. To what extent Rimbaud plans these elements or just accepts happy accidents in an aleatory, Cagean way, I don't know, but Rimbaud's instincts are spot on - his symphony of static provides a haunting accompaniment to the central text.

Harriet Walter's performance as the woman is particularly affecting. She speaks with the sort of voice you hear every day, on the train, in offices, in shops. In fragments she could be Bridget Jones: "You're right, as usual ... my pink dress with the fur on it ... and black hat ... Yes, I've still got it on ... No, I'm not smoking. I've only smoked three cigarettes ... But it is true ... But it is ..." With a different accent she could be Roz from Frasier: "Oh! Yes. I feel ever so much better. If you hadn't phoned I should have died ... No ... Listen ... listen ..."

Cocteau wrote that she should not be any "particular intelligent or stupid woman, but an anonymous woman", noting his intention to "avoid all cleverness [and] slick dialogue". He also set out to write an "unreadable" play, claiming that it was meant to be a pretext for an actress.

"The written work should disappear behind her playing," he said. Yet somehow, the intensity of The Human Voice script is all-consuming: Walter's performance drags the listener along, aimless but relentless amid the disturbing vortex of Rimbaud's soundscape.

The finished product is nothing like Poulenc, in fact it's hardly music at all - more a sort of ambient version of The Archers. The qualities in Rimbaud's work come from his keen ear for acoustic shading, colouring and transformation. They are powerful qualities, with the ability to move and disturb. Be warned: the "digital crud" that punctuates the work is realistic enough to send many listeners rushing to retune their radios: I suspect the BBC will receive a few complaints from people who tune in half way the broadcast. But please don't touch that dial - this is an inspired Between the Ears and a wonderfully cock-eyed choice for Valentine's Day.

`The Human Voice': 9.20pm tomorrow, BBC Radio 3.