David Ryder Prangley, Purple Turtle, London<br/> Ghosts, Water Rats, London

Anyone familiar with the film Purple Rain will understand what is signified by the phrase "a 'Beautiful Ones' moment". But for the uninitiated (and at this point I really ought to be forcing you to bathe naked in the waters of Lake Minnetonka), Prince, performing onstage in his role as The Kid, uses the song as a direct emotional address to his estranged girlfriend Apollonia, watching from the audience, who has deserted him and seems on the brink of choosing another lover. It's an intense, heart-wrenching scene, easily the film's finest sequence.

David Ryder Prangley, who is, if possible, an even bigger Prince fan than I (and I have the symbol tattooed on my arm), knows exactly what the phrase signifies, and his live show with The Witches is one elongated "Beautiful Ones" moment.

At which point, I sense the uninitiated scratching their heads once again. David Ryder Prangley (one of those surnames is made up, but probably not the one you think) grew up in the South Wales satellite town of Dinas Powys, and was musically reared by Cardiff's considerable hair metal scene. Decamping to London in the mid-Nineties to seek his fortune, the pixieish, androgynous Prangley assembled the glam rock band Rachel Stamp (named after a girl he fancied at school), who were snapped up, and quickly - after a handful of cracking singles and an unreleased album - spat out by the Warner Brothers machine.

Rather than curl up and die, DRP went DIY, and Rachel Stamp became arguably the biggest unsigned band in Britain, able to fill the Astoria with no label backing, and top the indie charts with their debut album. With their wickedly witty, hook-laden sleaze-metal anthems about sexual perversions and the like, they became the rallying point for an army of pink-haired, toy-jewelled girls, and boys who looked like girls.

A couple of years ago, Rachel Stamp went into hiatus, and David gathered a new band The Witches - currently recording their debut album with (Cure, Human League) producer Dave Allen - to back him on a set of solo songs. At around the same time, he went through a painful break-up with his long-term girlfriend. And this is where the "Beautiful Ones" thing comes in.

Heartbreak, much more than happiness, traditionally enflames one's creativity, and in DRP's case, it's true to an extreme degree. Every song he performs in his solo guise, excepting a cover of Roland S Howard's "Shiver" and something called "Space Station No 9", seems directly traceable to the break-up. And, as if to intensify things even more, the ex (with whom David is still close friends) has been at every single Witches gig to hear them. Knowing this, and being in their presence while the drama plays out - the accusatory growl of the couplet "you've gone and done it now/transmission is down", for example - and wondering what must be going through their minds is almost too much to bear.

Next to Rachel Stamp's primary splashes of Technicolor, The Witches - whose CV also features Placebo, Die So Fluid (whose female singer Grog duets with David on one song) and Killing Miranda - paint in shades of Rothko black. As Prangley, in a crochet top and girl's jeans, makes languid finger clicks, a spaceship-shaped guitar bouncing gently on his hip, their slow, sombre, oceanic rock is often so delicate it's drowned out by the Simpsons pinball machine.

His language is elemental, the language of being consumed and ravaged by love: the metaphors are typically about moths burning in a flame, or sailing on a sea of tears (although he's still glam-vain enough that his tears are "tears of black glitter"). But for all the uncomfortably naked emotion, these songs possess wit and irony: "Saint David of the Bleeding Heart" is a fantastically self-aware song title, and one verse, more than any other, captures the mix of flavours perfectly: "I've been contemplating suicide/But it really doesn't match my style/So I think I'll just act bored instead/Contain the blood I would have shed..."

Sometimes, this job feels like being at school. Glancing around the Water Rats is like morning registration: yep, he's in; yep, she's in... (and, in fairness, they're doubtless thinking the same about me). The music industry headcount is at full quorum tonight because one of its biggest hopes are beginning a three-week showcase residency.

The quartet, signed to Atlantic, snuck into the Top 10 of the BBC's Sound Of 2007 poll of music biz insiders. Looking at their tastefully-tousled hair (complete with the obligatory white-guy-with-afro on guitar), and listening to the sound they make, it's easy to see why those who have a vested interest in maintaining the status quo are getting as excited as Derek Acorah about the arrival of Ghosts.

Like that other marketing exercise in band form, Boy Kill Boy, Ghosts are a carefully-calculated composite. Is it Arcade Fire meets Supergrass? Is it Keane meets Editors? Is it Snow Patrol meets Doves? Is it all three? Whichever, there's something about them which makes you contemplate depressing questions. Like, is "poignant" just a chord change? Is "uplifting" just the interval of an arpeggio?

This is music made to be listened to by blokes driving Chelsea tractors on the way to watch Chelsea, before dropping a Chelsea bun round to their Chelsea Pensioner grandparents, and hitting a wine bar on the King's Road to chat up an American gap year student called Chelsea.

Mark my words: Ghosts will be huge. Maybe as huge at the Tesco tills as the chicken caesar wrap. This comes to you not as an endorsement, merely a factual report.

s.price@independent.co.uk