[jimmaswell]

Simple hypothesis re: music: our evolutionary advantage was our better brains that let us use pattern matching to understand things, so the brain evolved to reward pattern matching, and listening to music presents it with an easy exercise in pattern matching by predicting when the chorus will repeat, expecting chord progressions to be resolved, etc.

[dotancohen]

Your post really hits the mark for me. One of my favorite compositions is Beethoven's fifth, and I sometimes find myself identifying a new motif or combination of motifs in that work, even after decades of listening to it. It is a very rich piece, and the motifs develop slowly, simple at first but getting more complex in time. Not more complex motifs, mind you, but the same motif gains a few notes here and there, and sometimes shifts slightly. Very rewarding to find new ones, and only by reading your post do I discover that that piece challenges me actively, as opposed to more passive music.

The Wall and The Downward Spiral have similar elements of challenge, now that I think of it.