@TeamYouTube i got a copyright warning on one of my videos for the music, but not sure why, one of the two pieces i used was in your fair use library and the other was a parody made by another youtube that gave me permission to use it.
Your best resource will be the Copyright section of our Help Center, start with these top FAQs: https://goo.gl/FzBC2x . You can also review info on fair use, creative commons, and our troubleshooter linked from there. Hope these resources help answer your questions!