What is the difference between Copyright Form PA and Form SR?
In short, the answer is Form PA is for the copyright in the song (lyrics, melody) and Form SR is for the copyright of the physical recording of the song, also referred to as the master. That is the short answer.
However, the short answer probably leads to more questions like:
If you own the copyright to the song (Form PA), why would you need to copyright the sound recording if you already own the song?
First of all. copyright can help protect you from unauthorized use of your recordings, or
at least help prove ownership. Secondly, once you publish your song (make available for public purchase), anyone is free to make a recording of your song as long as they pay you mechanical royalties if they sell the song. I can just hear you saying,
"Publishing and Mechanical Royalties", what the heck are those?