Can I Upload Songs That Are in the Public Domain?
Any song or musical work that was published in 1922 or earlier is considered to be in the public domain within the United States. Although, if a copyright is still active on the original work, precedence needs to be given to the copyright. Understanding public domain can be a complicated matter.
Songs that are a part of the public domain are not automatically devoid of copyright constraints. The original score of the song might be free of copyright once it enters the public domain, yet other copyright elements related to recordings and more still persist. Sound recordings are not classified as a part of public domain in the United States due to elaborate concatenation of Federal and State Law. Thus, it's not allowed to sample public domain recordings.
Nonetheless, if you plan on recording your own unique version of an old, traditional song (originally published in/before 1922), you should be in the clear!
Note: When you distribute a public domain song, ensure to select "I wrote this song, or manage the songwriter (it's an original tune)" on the upload form when you're asked to.
Provided that you're absolutely certain that there aren't any other identified songwriters, you can name yourself as the songwriter of your own public domain work arrangement, or identify "Traditional Music" as the songwriter.