Crystal Castles are notoriously hard to pin down. They rarely do interviews, and when they do, they make those interviews difficult. Over half a decade of grumpiness, reticence and insouciance they’ve done little to promote their own work in the traditional sense. Instead Ethan Kath (scowler/knob twiddler) and Alice Glass (enfant terrible/screamer) have set about proving their punk spirit. A miasmic cloud of drugs, blood, spit and sex surrounds the band. Stories of danger and excess follow them like so many male and female groupies; some true, some half-truths and some probably just strung out by the band to foil eager journalists. Here’s what we think we know.

In Toronto, in 2004, producer Ethan Kath came across 15-year-old runaway Alice Glass fronting the noise-punk band Fetus Fatale. She was, to quote Kath, ‘higher than anyone I’ve ever seen in my life.’ Glass has her own rosy recollections from that time, including an anecdote about living in a punk squat with a man with an infected eye, who would fish his finger about in his pupil and poke it in other people’s faces.

They say that bad times breed good music, so Mr Gammy Eye should be thanked for the first sessions that produced, with serendipitous immediacy, some of Crystal Castles’ best tracks. Kath had given Glass a CD of fuzzy electronic tracks to sing/shout over, and when she turned up at the recording studio the sound engineer secretly taped the first of her improvised takes. The cut found its way onto a demo sent to prospective record label Merok. ‘Alice Practice’ as the song became known, was their first wave-making single, released to clamouring demand on a limited edition 7” in 2006. The band have since recreated ‘Alice’ for live gigs.

Glass’ wild performances have helped make CC far more than just a synth band. Showing a terrifying disregard for her own safety, on stage she’s a blur of sound and motion, clattering into the crowd/speakers/floor. In July last year she ended up in hospital with concussion after, she claims, being kicked in the head by riot police at Hard Summer festival in Inglewood, California. Kath, by comparison, plays a more subdued role in the gigs, hiding beneath his fringe and labouring over a battered flight case. It’s said that he lugs around a bank of interconnected, archaic electronic instruments known as The Brain, through which he channels the warped, 8-bit tones that define CC’s sound.

Kath’s technology, biography and personality remain mysterious, and likely will for some time. However, if you really want to know about him, listen to the production on their second self-titled album, released in May this year. Melodic, structured and emotional, Crystal Castles (II) could almost be dance-pop, except for the persistent electronic fuzz that rages through the album like a headache. And Alice Glass? She’s equally capable of producing punk anger and quiet fragility, and is the perfect match for Kath’s troubled electronics. There’s a darkness of the heart of their music that’s more dangerous and impressive than any tale they’ve ever spun or denied. And that’s why they’re so fascinating.

02 ABC, Glasgow, Tue 19 Oct.