Alice- Sadly, there's no way of knowing whether most songs are PD or not. In theory, anything that can be demonstrated to have been printed prior to 1900 is PD, but that doesn't stop Pete Seeger from copyrighting Cindy, or Peter Kennedy from copyrighting Greensleeves or Oscar Brand from copyrighting Yankee Doodle. You could probably defeat any of these in court if you were willing and able to take them to court .