A PRO is a Performing Rights Organization, whose business for songwriters, composers and publishers includes collecting their performance royalties. By law, PROs must send 50 percent of the total performance royalties to the songwriter's and composer's designated home addresses. The other 50 percent is the “publisher’s share,” and different PROs treat the publisher’s share in different ways.
For example, ASCAP requires self-published songwriters to start their own publishing company in order to collect the publisher’s share, which includes paying the large publisher set-up fee, setting up your publishing company’s bank account, and a ton of administrative hassle. BMI, in contrast, allows self-published songwriters to simply collect both songwriter’s share and publisher’s share in one lump 100 percent share without creating a publishing company.