When I listen to an album often enough, I get used to the sequence of songs. I'm sure everybody does. When one song ends, during the delay between songs, the next song begins playing in my mind. Once the song actually starts up, the one in my mind skips back to sync up and everything's happy.
When I listen to a compilation album, my mind frequently becomes confused, because the "next" song is not what I'm used to. This has always been true, and again I expect everyone experiences this.
But it's only recently that I've noticed that, once I've listened to a compilation album enough, each song has two "next" songs: the next song from the original album, and the next song from the compilation album. When the song ends, both songs start playing at once. Depending on which I'm listening to, one gets synced up and the other gets discarded.
I realized recently that, in the delay between songs, my mind rushes to remember which is the right next song. My mind hops back and forth between the two, first letting one dominate and then the other, forming a strange hybrid composition. And when the next song actually starts, if that's the one dominating in my head, the musical portion of my brain is at peace. If not, I feel a vague dissatisfaction.