The new way of generating hype on the internet is to pretend that a band comes from the stone age. No pictures, no story, just one or two songs wreaking havoc on YouTube. "We know Chvrches are two boys and a girl from Glasgow, and not much more…" said a music blog in July. It was nonsense, of course – a couple of Googles and you're reading lead singer Lauren Mayberry's winning entry for the Royal Environmental Health Institute for Scotland Journalism Award in 2010, a lively essay on the hygiene of body piercing. Or watching Martin Doherty playing synths with Scottish indie rockers the Twilight Sad – or Iain Cook playing synths with his previous band Aereogramme.

But there will always be mystery in that one-in-a-million pop song that gets you straight in the neck. Chvrches' The Mother We Share (released as a single on National Anthem in November) is a warm electropop wonder with the kind of tune Barry Gibb would've woken in the night to scribble down, and a lyric so touching and humane you want to take its birdlike but formidable singer out and buy her a hot chocolate. Over the Gary Numan-style synths and slick sound collage, Mayberry's high voice rings out with a rare untrained quality – that's why she sounds so Scottish, she explains, but naturally, "not like the Proclaimers".

"It's a question that keeps me awake at night," volunteers Doherty, a humble chap in a baseball cap at an 85-degree incline. "Do people only have a certain number of good songs in them? Do you write them all in the first year and then you have none left? I struggle with that!" There's a cautious glance from Cook. The most annoying thing about this "only two songs on YouTube" hype, he explains, is that people assume you haven't got anything else. Chvrches only formed a year ago (the boys have known each other since 2004) but they insist they've already got tons of songs – just that they're not signed, so there's nowhere to put them.

When you ask a band how their songs are written, they generally say they just happen when they sit in a room and throw ideas around and find what works, etc. Not that they use a "collaborative Google spreadsheet" to lay all their melodic contributions alongside one another, then trace the shape of a song emerging – or that lyrics are chosen for their proximity to an improvised set of nonsense vowel sounds. Chvrches' pop factory, rather like that of the other boy/ boy/ girl electro-trio the xx, seems both organic and scientific. And collaborative: nothing bothers Mayberry more than the assumption – which hasn't really been made yet, but she predicts it will – that the two blokes write the music and she sings it. "Even in the early stages, you can tell who thinks you're an idiot singing songs someone else has written for you," she says. "We never wanted to be two producers and a girl who wears some shoes. I'm not going to get on a soapbox and start banging on about vaginas but I'd hope that people are listening to the music."

The image thing troubles her. When you've recently completed a master's dissertation on images of femininity in women's magazines ("I spent a lot of time reading Cosmopolitan and quietly crying,") you're wise to photographers putting the focus on you and turning the rest of the band into fuzzy shapes in the background – she tries to stop them doing it, sometimes. If only Mayberry didn't look like she does – beautiful, startled and startling all at once – the path of life would be smoother.

Chvrches (they put the "v" in their name because they were "tired of competing with Jesus for internet hits") have already learned a lot about the industry by watching from the wings, and are fantastically analytical. Their hero Prince (they play his song I Would Die 4 U in live shows) has "no quality control" but they admire the way the purple icon was never "a perfectly packaged pop thing – he was messy. We are trying to keep things rougher too," explains Doherty. "Instead of quantising everything in a 'dance' way, we want to keep it rough, like demos."

Which is easy to do, until they've got a contract and a full-length record to make. "Albums are pretty much a marketing tool to get people to your shows now," says Martin, "but until we're signed it's like we are not a legitimate recording act." In the meantime, he admits to being "plagued" by melodies, while Mayberry works on her diaphragm to cope with the demands of their November tour.

One thing's for certain. You know you've made it when your parents aren't averse to the idea of you pursuing your music. "That was the first time I thought, maybe this band is going somewhere," says Doherty. "When my mum heard a song and said: 'That's all right.' She seemed surprised."