Welcome to filmmaking.net.

I, too, was curious so I used Google and typed in "free background music".
Wow, was I amazed. I had no idea there were so many places. Thanks for
the excellent question!

There is quite a bit of free music on the internet. The quality of much of it is pretty poor, though if you search hard enough you can find some good music. Besides free music, for non-commercial video there are many sites that sell royalty-free music for pretty cheap prices. There is far more choice on offer, and the quality is usually better. When you get on a bit further in your film, documentary and video making I suggest perhaps you look at this avenue for sourcing music. Here is a link to a tutorial I wote explaining what royalty free music is:
http://rocksuresoundz.com/2011/10/11/royalty-free-music-what-is-it/

Royalty Free Music and Sound Effects
Tony Koretz
http://rocksuresoundz.com

Hi, You can find here, free background music and more...
?url? http://www.musicscreen.be/Free-Stock-music/Free-Stock-Music.html?/url?

Your best option for free is creative commons music like incompetech, jewel beat is very inexpensive. You can find other with a "free royalty free music" google search.

Use my music for your film
http://danosongs.com

Feel free to use any of these Antiqcool creative commons tracks for your indie films. Some great songs....and they are free to download and use from our soundcloud page here. http://www.antiqcool.co.uk

Thanks for these links guys. Really helpful for what I'm working on atm.

A really good site:

http://incompetech.com/music/royalty-free/

Make sure you give credit

My site has cheap ilm soundtracks ?1 each www.soundscaper.net

Www.soundscaper.net - film soundtracks cheap with cleared copyright.