A nice source to find royalty free or public domain licensed music you might want to check out http://freemusicarchive.org/
"The Free Music Archive is an interactive library of high-quality, legal audio downloads. The Free Music Archive is directed by WFMU, the most renowned freeform radio station in America. Radio has always offered the public free access to new music. The Free Music Archive is a continuation of that purpose, designed for the age of the internet.
Every mp3 you discover on The Free Music Archive is pre-cleared for certain types of uses that would otherwise be prohibited by copyright laws that were not designed for the digital era. Are you a podcaster looking for pod-safe audio? A radio or video producer searching for instrumental bed music that won't put your audience to sleep? A remix artist looking for pre-cleared samples? Or are you simply looking for some new sounds to add to your next playlist? The Free Music Archive is a resource for all that and more, and unlike other websites, all of the audio has been hand-picked by established audio curators."