On paper, Goldfrapp are the last band on earth you'd go see on Valentine's Day. Romantic they indisputably are - their snow-capped, wide-open Alpine vistas and dark orchestral sweep conjuring the narcotised love-ecstasy of a thousand foreign films; their Cinemascope horizons as widescreen as a Morricone cowboy-opera, translated back into sombre, dark Europop; as chilly as the high-design-concept future-phobia of Arthur C Clarke and Ridley Scott, and yet as warm as John Barry's string-laden paeans to fragile humanity. But, clearly, we're half a world away from the bouquet and the chocolate-box. This kind of romanticism is tender, sure, but doom-laden; sensual, but with murderous intent. It's less kiss-me-quick than a kiss before dying, or a kiss before a kill. 'Unchained Melody' it ain't.

And if Goldfrapp are an abnormally visually evocative band on record, nothing quite prepares you for witnessing them live. Hair wound into a severe black wrap, leading a small, loud ensemble including writing partner Will Gregory on keyboard, Alison Goldfrapp stalks the stage on Valentine's Night with a nervous, caged-tiger physicality, her every gesture sharp, quick, abrupt, the kind that would usually accompany a clean kill: a swift ice-pick stiletto, a neat one-movement garotte.

She uses three mics: one of them quite normal, into which she murmurs with a lover's tenderness; the others sonically treated within an inch of their lives, so that, as she screams into them - her body rigid with the effort of thrusting out the breath - what we hear comes out sounding inhuman, artificial yet blood-chillingly evocative, like shreiking mechanised seagulls from a Michael Mann film. Dublin's gig-going lovebirds may or may not have been fully prepared for this.

But, as it turns out, just because the music is serious, doesn't mean that everything else is.

"Our violinist in the band is looking for a girlfriend," Alison Goldfrapp reports, brow furrowed with mock gravity, as we sit earlier that day with herself and writing partner Will Gregory. 'He's Italian," she adds.

Ah. Tonight could be his big night.

"It could be. We'll put him out front," says Alison.

"We'll make him play the recorder," threatens Will.

"Not a big one, either, 'cos me and Will have the two biggest ones. A descant recorder," says Alison, and they both titter. Ooh, not empty threats, you reckon.

Felt Mountain, Goldfrapp's debut, is, not surprisingly, the product of six months spent in a cabin in Wiltshire, overlooking a valley, flanking a forest, and - valley and forest apart - utterly cut off from the rest of the world. The two have a perfect foil-against-foil relationship - Alison small, prickly and direct, all elbows and frowns and studied slouching; Will more earnest, more still, completely helpful and solicitous despite speaking from behind a set of (slightly hilarious) clip-on shades, supplying sensible phrases for Alison to bang spikily off of. It's the sort of sparky, yin-to-your-yang, finish-your-sentences symbiosis that makes you want to go find a writing partner, for anything, right this minute.

Was it difficult to extricate yourselves from life and move to the forest to write?

"Well, both of us have been involved in music for quite a long time," says Alison, referring to Gregory's film-score work and her own collaborations with Tricky, Orbital and Add N to X. "I mean, we have done, you know…"

"Jobs,"' offers Will.

"The waitressing, and the…"

"Working in men's tailoring…"

"'Tea lady'…" Alison overenunciates thickly, making the phrase sound, bizarrely, like a euphemism for some manner of poisoner or nightmare-assassin.

"For half an hour…," Will giggles. Sorry, what?

"I had a job in a tailor shop, and it lasted, you know, almost… not exactly as long as that, but I'd say thereabouts. I think that a lot of musicians - I say this really just speaking for myself - are unemployable kind of people, 'cos…"

"No, I think you're right," drawls Alison.

"You know, we're living in our heads, it's... We're all but hopeless. Issues like… 'Is your tie straight?' - you know, these aren't things that…" He trails off.

Did you get sacked over some issue with a tie?

Alison cackles as the full extent of Will's tailor-shop shame is revealed.

"Yes," he says with a small sullenness. "And how to pay attention when they show you how to fold a suit, and every time you do it it would just crumple. I don't think I sold a single thing the whole time I was there."' He pauses. "I was sort of proud of it, as well."

As people say of cult artists ("everyone who saw them formed a band"), so hearing Goldfrapp's voice - especially in the flesh - is the sort of full-body shock experience that turns pop fans into pop singers. The effect is not a million miles away from the amazement with which people might remember watching Bjork's voice leave her lips in the SFX a few years ago. When you ask Goldfrapp when she realised she could sing, she becomes very still and quiet.

"Um…," she begins. "I can never quite answer that question."

Was there an age where you remember taking yourself seriously as a singer?

"Well I always took myself very seriously about everything," she giggles, and then goes quiet again. "'I was always interested in music, and I suppose I discovered singing through… being in the house, and being at a convent school, and having… a singing teacher who was very encouraging… towards me..."' She perks up a bit. "I remember the first time I sort of went to that class and was singing, and… feeling the top of my head buzzing," she says, hand on her head, "and going, like, Wow, this is really good…"

How old were you?

"Probably about nine. But my dad was a big fan of music, so um… He used to play a lot of classical music, and opera and things like that, and I remember hearing a piece of opera, and just… it making the hairs on the back of my neck stand on end, and thinking, Wow, you know, the noise of it. And the…" She breaks off, shaking her head. "Then I had some aspirations about being an opera singer…" She cackles. "But it sort of changed weekly… But yeah, I studied clarinet and hated it, and um… It's weird, cos music at school I just thought was really awful. I think I got more education from my dad than I did at school."'

Do you think Goldfrapp are an appropriate band for people to go and see on Valentine's Day?

Will considers this. Alison just laughs, slightly ominously. "I think… if you've got a realistic attitude to your relationship," Will offers, "that maybe it's not all good."'

"People do sort of snog, at our gigs," says Alison.

"Oh yeah!" remembers Will. "In Italy they really did," he says impressively.

"Yeah, in Italy, there was a lot of snogging going on," says Alison quite casually, as if people coming over all unecessary is a reaction that they provoke quite regularly.

Readers; lovers; smooching enthusiasts: over to you.