In a recent article asking for "homage or fromage?" on their official website, Sigur Rós is "saying 'no' to their music being used in advertising" and declare that they "never allowed their music to be used to sell anything", even though, apparently, they get asked a lot.
Nonwithstanding, Sigur Rós presents an interesting collection of advertisements that they think sound suspiciously similar to some of their compositions - which I can affirm - and critisise that copyright infringement in the music business can hardy be proved, since, according to their experience, it is sufficient to
change a note here, swap things around a bit there and, hey presto, it's an original composition, [so that musicologists will say] the chord sequence is "commonly used" or the structure is a "style-a-like" and not a "pass off", [leaving] insufficient evidence in the music to support a claim for infringement of the copyright.There is also a nice example given of an e-mail inquiry asking for a track for a commercial for Audi's Quattro system - which was denied - and later viewers of the ad discovered that "it sounds a lot like Sigur Rós" (see also article of "freelance copyrighter" Andi Bosselman).
For the song "Hoppipolla" (the one recognised by Sigur Rós fans in the Audi ads) there are three (further) examples of such "original compositions" given that, according to my - in terms of music copyright infringement, unprofessional - understanding, really sound "suspiciously similar". But listen yourself ...
The first video is an live recording of "Hoppipolla" (engl. for "puddle jumping") made during their 2007 Iceland tour (Heima), while the others are commercials.