RealAudio is sort-of a wav file. But it is it's own format and is streaming.

But I followed a link from the page you provided to the DoveSong site. that provides free downloads of MP3s made from old singles. If you follow some of the links you can find old pop songs from the 40s and 50s. Also some Stanley Brothers (got their version of "Man of Constant sorrow" there) and some Carter Family and Bill Monroe. Listening now to Bob wills' "Take Me Back to Tulsa". What a cool site! Thanks again!