A copyright basically protects the person or people who actually wrote the song. It has nothing to do with being paid royalties and is only used in a court of law when another party makes claim to the same song. In music there are basically two types of copyrights: Form PA (Performance Arts) and Form SR (Sound Recording). Form PA protects who wrote the lyrics and music. Form SR protects the finished mixed song and protects your song from being sampled and re-used by others.