There are sites like iTunes, Amazon, and others where you can legally buy music that supports the artists, and then add the music to your campaign. Also, many cities have local music shops where you can go and buy CDs which can be ripped to MP3. Additionally, a lot of libraries have music CDs available to borrow. Check out their soundtrack section, you might find some great music you could use. For free music online, try searching for Creative Commons music on google. Here is a good link to get you started <a href="https://creativecommons.org/about/program-areas/arts-culture/arts-culture-resources/legalmusicforvideos/" rel="nofollow">https://creativecommons.org/about/program-areas/arts-culture/arts-culture-resources/legalmusicforvideos/</a>