Tomorrow's Harvest, fans had to piece together a 36-digit code from six fragments embedded in radio broadcasts, Cartoon Network commercials, YouTube clips, online messageboards, cryptic vinyl releases and a projection in the art gallery opposite London's Rough Trade East. It speaks volumes about the dedication and know-how of the duo's fanbase that they were energised rather than frustrated by this multimedia scavenger hunt. The degree of obsessive analysis and theorising on the fan forum Bocpages.org/wiki would shame a Talmudic scholar. Michael Sandison and Marcus Eoin, Scottish brothers who spent part of their childhoods in Canada, affect people in peculiar ways. The mysteriously moving musical language of memory and loss they established on 1998's cyber-pastoral Music Has the Right to Children has seeped far and wide, from chillwave to the muted dubstep of Burial, from cloud rap to the "hauntological" output of the Ghost Box label, while being pretty and accessible enough to make sense in the background of Top Gear or CSI: Miami. Fellow 70s kids might have detected echoes of certain phenomena from their own youth, such as public information films, educational documentaries, the BBC Radiophonic Workshop and obscure British horror movies. But through their deployment of certain sounds – detuned analogue synths, snatches of indecipherable speech, and hazy production which sounded either sun-bleached or water-blurred – Boards of Canada managed to universalise that sensation and evoke the sound of nostalgia itself, defined by academic Svetlana Boym as "a longing for a home that no longer exists or has never existed." g With 2002's less benign Geogaddi, animated by an interest in religion, mathematics and numerology, the duo attracted the kind of people who spend long nights investigating the internet's more arcane precincts. However loudly the brothers protested that the decision to make the album 23 tracks and 66:06 minutes long was merely playful, fans probed it for occult messages, enticed by its backwards-masked vocals, eerie samples and mood of creeping paranoia. Through such magical thinking a cult band came to resemble a genuine cult.