Sorry for my rant and maybe PG should address this in a thread. If a moderator is reading this, maybe they will do exactly that.

A "cover" is pretty simple. You are performing a version of a song written by someone else, who more than likely has registered this song with their PRO (BMI, ASCAP, etc.) and has filed for copyright. You do not own the song or control anything, they do. You cannot record your own version and post it online unless you pay the license fee. (If it is a YouTube of a live performance that is a mechanical license, but everyone who is posting songs needs to read the laws in their country, and the countries hosting platforms where they are posting. There is a lot to know.)

In the United States, at least one PRO has bounty hunters combing through bars and nightclubs and restaurants with open mics to see if anyone is playing a cover song of a BMI artist (let's say Neil Young, I don't know if he's BMI or ASCAP) and if they are and the club doesn't have a blanket license from Neil Young's PRO, they can get (and have gotten) fined many thousands of dollars PER INCIDENT. Enough to put the bar out of business. That's why bars freak out if you start playing a cover song and they don't have that license. They will yell at you and throw you out. They can't afford it. Those bounty hunters get paid on commission and they are as aggressive as flies.

Now, again, unless you are a lawyer, you should not make random assumptions about the reasons for the PG rule; you know they have lawyers they have consulted on numerous topics, including this website, and you have to know there is a solid legal reason for every request they make.

It is the same reason you can't legitimately buy a BIAB file of a popular song with the melody line midi in there. That melody line is under copyright protection. It is against the law. People are starting to crack down on free midi files more and more by the way, and that is why you see them less and less, unless you buy them.

Copyright law violations are not a joke.

Hope that helps.