Any recorded song is legally divided into two distinct entities: the song itself (the words and music, written and composed by an artist), and the Recording (the actual recorded interpretation of a given song).
This means two separate companies are involved in clearing rights for a song, and each is entitled to receive royalties on the part they own.
Music Publishers own the song’s copyrights (words and music), while Record Labels own rights to a recording (be it a studio recording or a live recording).