A video without audio is likely to be flat and boring.  Adding the right music as a background can create mood and excitement that can make or break the viewer’s experience.  Unfortunately, YouTube videos are not showing without sound.  Why?  Because the soundtrack used is copyrighted, and the maker of the video did not have permission to use it.  Be careful not to break the law by putting someone’s music track beneath your video is you do not have the right to do so.

There are various ways to get music tracks that you can safely use.  One way is to make use of the music shared on sites such as Creative Commons, Incompetech, and Jamendo.  On these sites, the creators share their works with the public.  You might also try finding some at sites that have stocked libraries of classic music and loops, like iStockPhoto.  You could tap into the membership site TwoBuckThemes, and get 5 loops each month for $10.

However you find your music, just make sure that you have the right to use it publicly, and there should be no problems.