they have a rating system, that rates the songs by popularity, very complicated, you can guess about the top 100 hits and album sales but what about a song like happy birthday, which I think is still under copyright or it ended in recent years.
Not a big seller not played on the radio alot but alot of live performance.
If you record a song that has a copyright you have to pay x amount per song times the number of copies you are printing, not just whats sold.

[This message has been edited by mikeathome1 (edited 01-07-2005).]