When I graduated high school, I earned a living by transcribing audio recordings (usually cassette or reel-to-reel) by composers, songwriters, arrangers, performers and even jingle writers. It was very exciting to experience these early versions of pieces - some of which eventually became well known. And it was great ear training practice.
Then in 1976 it all changed. Congress passed the Copyright Act of 1976. This new law (Public Law number 94-553) greatly reduced the hassle of copyrighting music. All you now have to do is submit a recording of the piece in almost any and all formats. That law also created a new symbol to designate protection, ‘P’ in a circle ℗. The ‘P’ stands for ‘phonogram’ which is another word for the phrase ‘sound recording.’ You probably never noticed but check out the symbol on a CD that was manufactured in the last few decades. It’s sure to be a ℗ not a © .