There's tons of great music that's free to use and it's largely unrepresented in the world of video art. Find a song that's openly licensed or in the public domain to use for your video.

How to search: You can go about this in several ways, such as through an advanced search on Google or Yahoo! where you can specify by permissions for reuse, or search directly at music platforms and libraries that host Creative Commons-licensed music and music that is in the public domain. 

• Creative Common Search Portal: http://search.creativecommons.org.

• Search music communities for CC-licensed music: http://creativecommons.org/music-communities.
• Check out record labels under CC licenses: http://creativecommons.org/record-labels
• Vimeo, has free CC-licensed tracks in addition to paid-for tracks: http://vimeo.com/musicstore.

These are just a few examples of places you can look for openly licensed music. There are six different CC licenses, and other open content licenses to boot, and that they are not all the same in their conditions for reuse. Also, "Under CC licenses, syncing music in timed-relation with a moving image is always considered an adaptation," so you would have to find music that is under a CC license that allows derivatives.

For more information on the CC licenses, see http://creativecommons.org/licenses.