Role definition in co-writing: who holds melody, who lyrics, who structure, who production. Each contributes where strongest.
Divide roles before session: 1) Melodist — creates vocal line. 2) Lyricist — writes words. 3) Structure watcher — guards song form.
Clear roles prevent conflicts and increase efficiency. Everyone knows what they're responsible for.
In Nashville, the standard is: one writes lyrics, one melody, one production.