Just to follow up on this. Here's a recent post from CD Baby that may also help clarify this. We are talking how to collect mechanical royalties for streaming sales of DiY releases..

"Mechanical royalties are especially challenging to collect for DIY artists. These are collected for sales and interactive streams by Mechanical Rights Societies that, in most cases, operate separately from the performing rights societies in a particular country. Without a publishing deal, or working to affiliate yourself with several global mechanical societies, your mechanical royalties from streaming and foreign sales are going uncollected. They sit at the mechanical societies, waiting for you to claim them. A writer/publisher can attempt to affiliate with all of them (at great cost in both time and affiliation fees) or work with one publishing administrator who already has a relationship with these societies. With a the assistance of a publishing rights administrator, you collect EVERYTHING you are owed, minus a small commission."

Source: http://diymusician.cdbaby.com/2015/...source=facebook&utm_campaign=general