Before the copyright
intellectual property was preserved by common law. Then the copyright concept allowed one to own the intellectual property they created. The copyright developed its own lengths for protection and who, what, and when the copyright can vest are ever changing issues. There was even an international agreement about this issue.
Public domain traces its roots to the copyright movement when the printers in Europe introduced concept of ownership of an idea or intellectual property. Copyright law was one of the first laws passed in the U.S. in 1790. When the copyright expires, the work enters the public domain.
What actually happens
There is noone with a copyright to enforce. So you are on your own. A correct use of this public use should not have anyone trying to enforce the copyright. Of course the person (usually a publisher) who has collected monies on behalf of the copyright hates you, Free use is the last thing to encourage, and will still try to collect on this earning copyright. The music composition has two copyrights one covering the composition and another covering the sound recording. They are referred to as the circle “p” and the circle “c.” They represent the both of the copyrights in musical compositions. So after you are convinced the music use is what is yours by law, please don’t expect anyone to inform you. If the intellectual property is in the public domain, no one will have standing to enforce anything.
So i recommend doing your own research
as to whether the intellectual property is in the public domain. This research will help as a precursor to a potential challenge to your use.
Once you have ascertained the music was in the public domain
use it for what ever you want and wait for no one to enforce the copyright,
One rule of thumb,
In any country music made before 1923 is in the public domain.
Fortunately for music
the phonograph had been in invented years before.
This is an example of a song in the public domain by virtue of the date. 1923