Like, there is song which I don't want, constantly reverberating in my mind. I've two questions.

  1. Why it I reverberating in first place?
  2. How to get rid of it?

Not an answer from texts, but from my own practice: what I noticed is that certain songs start playing in my head when my "subconscious" mind (which is pretty conscious these days, but usually sits in the background) wants to communicate some concern or sentiment to the rest of "me". So it starts playing some song with a certain message in its lyrics. I swear I'm not making this up, noticed many times. And most of the time the message is pretty obvious and is related to some suppressed concern that bothers me.

In order to stop it playing, I just have to stop ignoring it and acknowledge receiving the message. Think about the issue. Then the song stops.