This Alex Ross article from The New Yorker is worth reading.  It tells of Pristine Classical, a place where you can get extraordinary remastered historic performances of not only Blind Lemon Jefferson and Robert Johnson, but also Toscanini's 1947 Otello, Willem Mengelberg's "swaggering" 1941 take on Strauss's "Eign Heldenleben," and so on.  Very impressive.  Here is the site: Pristineclassical.  You will hate yourself and if you don't visit and listen and download.