ProjectXerxes
I've Got It
If something is royalty free do you need to worry about contacting the producer or giving credit?
You don't need to contact the Publisher as it is Royalty free Stuff!
and But if the publisher requests for giving credits then do give them credits... 
But Be sure you cross check before you use those so called Royalty free Stuffs.. You never know they could be copyrighted! 
Nope! Usually there is still a copyright on royalty free music. If you take the Creative Commons BY license it allows you to use the music for free i.e. without royalties but you have to credit the artist in the way he demands.Nope! Royalty free is basically non copyrighted music, ...