I constantly listen to the same band over and over again when i am in a manic or depressed state. I have found that the songs take on a completely different feel depending on my mood.
I was recently listen to a band called Apocalyptia when I was depressed and one of their songs haunted me. It was a song called "Beautiful", it is a hard rock meets classical with no lyrics, but in my depression I could hear the sorrow behind the notes. Then the next week when I was a manic state, I listened to this song again and it was a completely different song, I could hear how beautiful it was and the joy between the notes leapt out at me. I couldn't believe how much it had changed just because of my mood.
Another song that I used to listen to non-stop when I was a teenager was "Low Man's Lyric" by Metallica, that song help me through a long depressions