In the United States, The Harry Fox Agency is the Mechanical rights agency for songwriters and publishers.
They issue the mechanical royalties for songs, keep track of them, make sure the users pay, and provide statements to the publishers. They charge a set percentage of gross royalty collections for their service.
One thing I saw on their site and did not know is that Jonathan Cain AND STEVE PERRY are both listed as writers on Faithfully. I guess the credit on the Album cover itself only represents one aspect of who receives a royalty for writing. Even 1% counts in the royalty game, so it could be that Steve asked Jon to make a tiny change on the song that got him his cut.
There's a public search feature on the site if you are interested in doing your own research.
http://www.harryfox.com/index.jsp