Whenever possible, consider using your own music or music that is published with a license that allows you to use it in your movie. Copyright Free does not mean there is no copyright, It means a license has been selected by the creator that allows you some access to the work. These licenses are called Creative Commons licenses.
Every Creative Commons license requires giving appropriate credit. They all include, at the very least, "Attribution," which means you must give credit to the creator of the work.
T A S L
Title, Author, Source, & License
Music: "Tra-la-la" by Podington Bear
From the Free Music Archive
Music: "Comfortable Mystery 2" by Kevin Mcleod
From: http://incompetech.com/music/royalty-free/index.html?isrc=USUAN1100537