Have you heard of SoundCloud? It’s a website that has music creation and sharing tools for artists and fully supports Creative Commons licensing. That means you can do a search for “Creative Commons” and locate tracks to accompany your multimedia documentary legally. Check it out: http://soundcloud.com/
Another great resource for locating CC music is http://www.jamendo.com. If you go to “Advanced Search,” you can filter for CC licensed tracks.
Check out ccMixter to find sound and samples that you can legally use, mix and mash, as long as it is for non-commercial purposes. http://ccmixter.org/about