it's the album - it's just a really, really good compilation and this song is part of it. the song on it's own is strangely melodic, but in combination with the other songs on the two-disc album becomes something meaningfully melancholic.
I was skipping this song, too, until I heard the original by Blind Willie Johnson. Now, I understand this version. Let's just say that if you are feeling vulnerable or it's dark outside, don't listen to it unless you want to *feel* it. It's fairly creepy yet mesmerizing. I just can't get Johnson's humming out of my head.