Here's a thread borne from a post in another thread - it started in the "school band/copyright" thread.
I came across some truly remarkable old tracks, all public domain, which you can download and load into your music catalog app for free.
http://www.publicdomain4u.com/
When you have some spare time, check out Blind Blake, Leadbelly and some of the others. This stuff is priceless.
Best,
Kurt