In an attempt to make its Creators more aware of the issues they may fall foul of if they upload videos with copyright music tracks on them, YouTube has unveiled a new search tool to solve the dilemma.
Looking for a specific track in YouTube’s Audio Library will now provide details of what restrictions (if any) will apply to your video once it goes live as in this example:

Meanwhile the Google-owned website is urging Creators to use music tracks from its “free use” selection which have no such restrictions.
Full info at youtubecreator.blogspot.com/2014/12/mystery-solved-what-happens-when-you.html