I first heard this song (although a slightly different version) at the final scene of the movie Vanilla Sky. "I'm frozen, and you're dead. And I love you." I've always thought this song was beautiful, but I used to think it was atmospheric background music, which I'd play while lighting incense and reading or playing video games. Then at one point, when I was feeling especially sad, I listened to this song, and it absorbed all my feelings--they were simultaneously nonexistent and amplified--the music overcame me and it was like I was in another place.
This song is off Sigur Rós's third album, untitled (), released in 2002, which contains eight untitled tracks, although the band has created working titles through their touring (see the album's story here).
The music builds and moves in such a way that you'd swear you were on a journey. When the guitar peaks, it's as if the clouds open up to let the light in. It's a pretty amazing moment.
Upon first listen, I thought I knew what they were saying in this song, and you might have some ideas yourself. But the band made up their own language for this album, which they call hopelandic, and since it's nonsensical it simply serves as another instrument. But trust me, you do not need words to get into and enjoy this music.
I made a mix of sad songs for a girl once, and she told me this song didn't fit, because she thought it was a happy song. It turns out the band views this as one of their optimistic ones as well. I still hear it as both. Either way, it's definitely an emotional song, especially if you allow the music to surround you and pervade your thoughts.