NOTE: It should be remembered that sometimes musicians do take works from public domain and create a new arrangement of the original work, thereby also creating a new copyright that protects that arrangement.
it is the legal responsibility of the person creating a new arrangement to ensure the original work is not protected by copyright. If the original music is in the public domain, a new arrangement of that work would be entitled to copyright protection as a derivative work. As with new arrangements based on copyrighted works, the copyright of the arrangement protects only the changes or additional original creation of the new arranger. Even though the original work is in the public domain, copyright protection still does not cover the original work upon which the arrangement is based.