I have no idea. For me, context plays a big role. For example, once I was at school in the courtyard with some friends. It was an otherwise normal day. I remember the weather was good. A friend had the radio on as he was loading the kiln for a firing and over the local college radio station a Godspeed You! Black Emperor (though I think at the time, they were still Godspeed You Black Emperor!) came on. I have no idea what song it was, but what I do know is that it completely changed the quality of the scene. The sun seemed different as did the air. Everyone in the courtyard, all three of us felt it and asked each other if we'd been affected by the song and as far as we could tell, we'd all been affected in the same way. A week or so later that same DJ played the same song and that time nothing happened. But at that particular moment in the courtyard, that song was exactly what needed to happen and in that brief span of time, for me and two other people it was a perfect song.