What a producer agreement actually decides
Four things: what the producer owns, what the producer is paid, when the producer is paid, and whose name is on it. Most producer agreements handle the second one carefully and the other three by accident.
Who owns a record: masters, publishing, and why they are two different things
Every song you can hear is two copyrights, owned by two different sets of people, paid through two different systems. Owning your masters is one of them. The other one is usually worth more.