This is a very interesting topic to go through. I have actually done this a couple of times, and to be honest, there are even some songs that can be used like this. It's very easy to continue in denial because it is not technically "watching pornography", however we are clever fools; we can justify the substitution in our minds!
Of course it is. Sound is arguably more important than the visual. You can prove it to yourself by watching a creepy ass horror movie with no sound. It won't even be scary. There is as much power in audio then there is video.
Oh yes. My husband would look up sexy music with females moaning in the background to M to. Same as looking at it. It's nothing but empty sexual stimulation getting to the dopamine high, replacing all connection with real people.