I mean, they're already scatting in a nonsensical language (Vonlenska aka Hopelandic in English) that may be post-rock's answer to Klingon. Which already makes them superlative in my book. As their site explains:
on von, Ã¡gÃ¦tis byrjun and takk, jÃ³nsi sang most songs in icelandic but a few of the songs were sung in 'hopelandic'. all of the vocals ( ) are however in hopelandic. hopelandic (vonlenska in icelandic) is the 'invented language' in which jÃ³nsi sings before lyrics are written to the vocals. it's of course not an actual language by definition (no vocabulary, grammar, etc.), it's rather a form of gibberish vocals that fits to the music and acts as another instrument. jÃ³nsi likens it with what singers sometimes do when they've decided on the melody but haven't written the lyrics yet.
But when NPR's Bryant Park Project invited them on their show, there was no scatting at all; in fact, the only thing in abundance was the sound of a scrambling host and maybe some tumbleweeds. Some people sided with Sigur RÃ³s, and some with the host, but go ahead and judge for yourself here. And if you've been in the position of interviewer, did you ever have any subjects who were particularly nonplussed?