Why do songs lose novelty when listened to repeatedly?

I once went to a lecture on consciousness by a philosopher and he discussed how the mind or awareness is geared toward perceiving differences or the new. He doubted that you could actually be "aware" if all you were ever exposed to was a consistently blue expanse of sky with no clouds or variations in color. (this was years ago and his explanation was probably way better than my paraphrase)

This is also probably related to the fact that your mind is automatically ignoring all sorts of repetitive sensory inputs that it learns is "normal". I've noticed this when I get new glasses with different frames and at first the new frames are noticeable but that quickly fades into the background. If you ever listen to classical music the theme or melody is not just repeated the same across the song but has variations then often returning to the original notes. Following that across the song is part of the appeal and just repeating it would be boring.

Sometimes it comes back. There's an album that blew my mind in the early 80's. By the 90's I was kinda losing steam on it, and didn't listen to it for a while.

The musician has released a number of other albums in the meantime, but lately they pretty much all sound the same, and lack a lot of the dynamics that I remembered.

Recently I listened to that earlier favourite, and again it blew my mind. As much as fans suggest otherwise, this musician was significantly better at the beginning of his career. Going back to that first album after a long pause totally sold me on that.

So if you've lost interest in something that used to blow your mind, give it a rest for a while. Like years. Then come back to it and see what you think.

We could ask the opposite question:

Some forms of entertainment are usually only entertaining the first time. Like jokes. Or movies.

Music seems to be a form of entertainment. But usually we are quite happy to listen to a new song more than once.

So why is that?

This may sound trite, but that follows from the definition of "novelty".