It seems almost too good to be true. I'd love to have Robert Johnson on my soundtrack.

http://www.publicdomain4u.com/

It's probably not..

I used to listen to a lot of old blues and Blind Blake was my favorite. If you get a chance listen to him...amazing guitar work! He sounds like 3 guitar players at once...definately the best guitar player of the era!

It's possible that it's legit, but there's no way to tell from the website.

These are early recordings. Pre-1978, term of copyright was limited to 28 years, with a second term of equal length available only upon renewal. Lots of works lapsed into the public domain when the copyright owners failed to file the renewal.

Sure the copyright on the music itself might be ok to use, but maybe not the recordings that are on that site. Two different copyrights..

This web site suggests that the best rule of thumb is to assume that NO recordings are in the public domain:

http://www.pdinfo.com/record.htm