The Art of the Deal refers to the negotiations regarding the transfer of “the rights of publication” from the person who created the work (the author) to another person or company who can monetize those rights, usually, the music publisher, or recording company.  This transfer can be for a period of time or for the the duration of the rights involved.  

The rights being transferred are the five (or 6 in the case of a sound recording) exclusive rights under federal copyright statutes that attach to any and every original work.  These include the right to copy the work (copyright), the right to publish the work (to distribute it, share it, give it away, sell it, market it), the right to control the public performance of the work, which is what ASCAP and BMI – Performing Rights Organizations (PROs) – collect for), the right to control the public display of the work, and the right to make derivatives of the work (a movie from a book, a ring tone from a master recording, a translation of the song).   

If you write a song you have the rights of a music publisher.  If you record music you have the rights of a recording company.  Artists or bands who do not wish to run these companies.  They may receive an offer from someone who does that they can’t refuse.  It’s difficult to be a successful performer and to also distribute and market music, so rights are shared and transferred.