When you say "actually hear", do you mean that the only way you could tell that the sounds weren't real was that you knew (for example) the radio was off? Or do you mean something else?

I would describe my related experiences as my imagination producing background noises. If I tried to concentrate on the background noises and bring them to the foreground they disappear and I only have the non-noise version left in my head. My hunch is that this latter state is more common amongst people who get songs stuck in their head: You think of words, you think of melodies, but you do not hear anything.

Another easy way to show the distinction, I never sing along with the fake audio. It is always background and as soon as I notice that I am hearing something it goes away. The experience reminds me of deja vu to an extent. I can tell something is hiccoughing in my sensory processing but instead of complaining about it I just enjoy the song as long as I can before it goes away.

Obviously, I cannot speak for Vladimir_Nesov.