By role
Which royalties are yours?
What you are owed depends almost entirely on which side of the release you sit on. Each of these covers one role: where the money comes from, and the one stream that role most reliably leaves behind.
Producers
Most commonly missed: the producer who never registered as a writer.
Songwriters
Most commonly missed: registered with a pro, invisible to the mechanical side.
Small Labels
Most commonly missed: the label that registered its artists but never itself.
Managers
Most commonly missed: the gap that generates no paperwork.
DJs
Most commonly missed: the set you played and never reported.