This is interesting and I think the analogy to playing a song in your head is a good one.

With regard to how visual the minds eye is, I have this anecdata:

For me, when I’m visualizing mentally, usually with a memory, replaying something, I stop registering what my eyes are presently seeing. No visual memories form of what my eyes were seeing while I was absorbed with reliving the memory or visualizing some idea.

I have to be careful about this when I get bored while driving.

I'm aphantasic, but I can relate to almost going blind with inattention. Not like I now have a black visual field, but just losing awareness of what is actually in it, like it is some sort of matte painting put up during intermission. But there remains some lower-level processing, because I may reflexively kick back into full seeing due to some unexpected change.

For my "mind's ear", imagining sound is not quite as rich as hearing, but quite similar. I can even "feel" aspects like bass thumping my chest or my ears tightening up due to an imagined or remembered loud noise. I can nearly feel dampness on my skin if I remember the roar of a waterfall.

Still, it's a bit more hollow than real hearing. Also, it is nearly a second channel of sound processing. I can have music playing on speakers and then think about a different song. The one going in my mind's ear does not mute out the real signal from my ears, nor do they really blend together. If the real audio is loud or catchy enough, it will derail my effort to sustain the secondary imagined program.