One of the features I've loved about last.fm for a very long time has been how it let's you tag your music. It gives you a list of your popular tags and also a list of popular tags other folks have given the song you're about to tag. Often the top tags are the kind you'd remember seeing in a record store when there were such things (I assume they exist, but I hardly shop for records anymore...gosh, that's sad.) Anyway, they had and probably continue to have dividers each with a label describing various types of music. The top ones, as you'll see are usually pretty good descriptors, but a little bland. A little ways down though and you start to get to the tags that seem to just speak to you, as if to say "that hits the nail on the button!"
I'm sure machines and machine tagging will eventually learn to be creative and hip in labeling things we need to find more easily. Personally I can't sit around and wait for that... but in the meantime I'll just continue to label things the way I've always done, in my own words.
BTW - I have no idea what Jonsi is singing about in this track, since some of it is in Icelandic, so "great lyricists" is tongue-in-cheek...as it is when I usually apply it. Maddy, my seven year old, sings the song word for word with what sounds like perfect Icelandic inflection. Could be at that age, the live inner elf helps with that sort of thing.