Hi, I have a free royalty free music library at http://www.danosongs.com/ which uses the most friendly creative commons attribution license.
You only need to credit me and you can include my music at no cost.
There are over 100 songs there in various styles and I release new tracks several times per month.
DanoSongs Royalty Free Music
Hi, here is my latest free backing track, it is an acoustic guitar instrumental: