I may have misinderstood your question but here's my answer:
When you say producer
Producer could be me with some money to pay for whatever product I need.
Like in a movie. Executive producer is the one that actually owns the money.
The producer is the one that got the money from the executive. The producer then is in charge of this money.
The producer's job is to find the right people for the job and make the money for the executive.
On the music part:
When you're a music composer and you meet the "music director" remember that the music director works for the producer who does the work to make the executive happy.
If you offer the music directly to the "client" the "client" (this could mean the misic director or could be anynody) you either make the clause of use or you are offer a deal. It is up to you.
This could mean them buying the right of your music. Or just paying to use the music in specific ways for specific amount of time or use. Royalties may or may not be included.
I hope this helps you understand better.