Hardly a day goes by where Sigur Rós's glacial soundscapes are all over British television whether as part of a documentary or as the musical livery of a programme or strand, and confirming it as one of the emblematic musical signatures of its era. For the last year or two, it's been Sigur Rós's heavenly "Hoppípolla" (recently used to trail BBC1's Planet Earth series) that can't be avoided.

You've all heard it hundreds of times: that tentative piano figure cycling around and around, seeming to climb up and up expectantly like an MC Escher belvedere, until it finally reaches some emotional tipping-point and brims over, cascading in soul-lifting waves of fulfilment as strings and brass crowd round to hymn along.

Tracklisting Index

• Glósóli
• Við spilum endalaust
• Hoppipolla
• Untitled #1 (vaka)
• Sæglópur
• The Nothing Song (Vanilla Sky/Njósnavélin)
• Svefn g Englar
• 'Heima' (At Home) Film Trailer
• Viorar Vel Til Loftarasa (Subtitled)

It's become utterly ubiquitous since its release in 2005, as directors discovered how perfectly it seemed to suit all manner of situations, from baby whales being reunited with mommy whales on nature programmes, to some clueless pleb finally mastering a meaningless task on any of a hundred bogus reality-TV shows. Look! She's managed to run that half-marathon! Cue "Hoppípolla". See! The courting swans entwine their necks! Cue "Hoppípolla". Wow! He's not just conquered his fear of flying, he's enduring barrel-rolls! Cue "Hoppípolla". Gasp! It's the winning goal, in slow motion! Cue "Hoppípolla". And so on.

By last year, it was almost possible to channel-hop randomly and never hear anything else. It was even used in an episode of Doctor Who, and more recently in trailers for Slumdog Millionaire. And Oxfam adverts. And The X Factor, the audio equivalent of sleeping with the enemy. Small wonder that when Sigur Rós were recording it, they gave it the nickname "The Money Song" – they immediately gauged its appeal – before settling on "Hoppípolla" (Icelandic for "jumping in puddles").

You can hear why it's so popular among programme-makers. Because Jónsi Birgisson is singing in his native language, it's not stained by lyrical associations, while it fulfils our current yearning for aspirational sonic euphoria. It's like Coldplay minus the simpering-twatness, Radiohead minus the bitter curmudgeonly aftertaste, U2 minus the overweening egotism. It's the perfect musical soundtrack, it seems, for a UK blinded by vague empathy as it hurtles towards bankruptcy.

But it's not, Birgisson claims, as ubiquitous on Icelandic telly as it is here. "No, that's definitely a British thing," he says. "Everything dramatic and 'Hallelujah', every dramatic ending – cue it up!" (I'm not sure, in retrospect, whether he's referring to that "Hallelujah" or is using the word as an emotional analogue and has, spookily, simply stumbled across TV's new-found replacement for "Hoppípolla".)

"Hoppípolla" thrust Sigur Rós on to an entirely new plane of fame and fortune. The album from which it was taken, Takk..., was their fourth full-length outing, its predecessors having appealed predominantly to a refined art-rock constituency. Their debut album Von, for instance, sold a grand total of 313 copies in Iceland when first released in 1997, only accruing popularity when it was reissued in the wake of subsequent successes with 1999's Agætis byrjun and 2002's (). Since then, they have earned vast sums from their art, a position ironically exaggerated by the recent financial upheavals in Iceland. "Because we get our salaries and stuff from England, and the krone to the English pound has just doubled, it is actually good for us personally," explains Birgisson, with slight embarrassment. "But for the people around us, it is not good."

So how would they themselves describe their music? "I think the words that come to my mind are, like, 'organic', maybe," Birgisson eventually concedes. "There's something quite natural about it, and we think a lot about soundscapes when we are doing it. Basically, when you strip everything away from the music, at its quietest it's normal pop songs; but it's the way that you produce it that puts the meat on the bones of what you do. But it's always hard for us to describe how we sound."

Most bands, if pressed, will make similar claims on inexplicability, but in Sigur Rós's case there's more justification than most, their music being less permeable to descriptive, physical comparisons than abstract, emotional comparisons. And even then, they seem to have the gift of finding the gaps between emotions, sometimes leaving the listener adrift on a sea of conflicting moods and vague yearnings. In terms of instrumentation, however, they have shifted more towards using acoustic sources than electronic ones, particularly on ...endalaust. This, it transpires, was more a matter of convenience when they found themselves in unfamiliar surroundings.