Caveat: previous posters here are correct that the compulsory license only kicks in once a recording of the song has already been published. I can't, for example, go find the first song Paul Simon copyrighted and record it, if it has never been recorded before. This restriction has the effect of forcing the first person ever to a record a given song to get direct permission from the composer--unless he or she IS the composer. Once that first recording is published, others can record it simply by paying the licensing fee.