Jed, for a song like your "Ballad of Thomas Higgins" where the lyrics are original and the melody is traditional - how do mechanical and performance royalties work?

My understanding is that when one person writes the lyrics and another writes the music they each get 50% of the royalties, but if your "composer" is tradition rather than a specific individual, then do you get 100%? Or do you get 50% and the other 50% isn't owed to anybody?

Thanks, Marion