Music rights for podcasts break down into two separate copyrights you have to clear before you use a song: the composition (the song itself) and the sound recording (the specific recorded version). A standard public performance license from ASCAP, BMI, or SESAC doesn’t cover either one for a downloadable or on-demand episode, so most podcasters end up needing a synchronization license and master use rights, or a pre-cleared royalty-free catalog that already includes both.