You can only have covers if someone 'owns' a song. In traditional and classical music songs are free and can work for anyone! We don't do 'covers' we do 'versions'. People bring their own vision and interpretation to a song or tune. They go on doing this for years (in the case of Early Music, centuries) after the music was written.   The idea that a song is the property of the original performer and that any subsequent performer is merely copying arose when recording became possible.