My friend Wynn sent me a link to an internet archive, which is working with Boston Library, to digitize record album which are supposedly in the public domain. I decided to start with comedy albums to see what was there, and what I found made me wonder if Flip Wilson's Cowboys and Colored People, which has the famous Christopher Columbus routine, could really been the public domain. And for fans of The Fabulous Mrs. Maisel, of which I am not a fan, as readers may recall, there are a few Rusty Warren albums. It is amusing to me that many people think the show is based upon Joan Rivers. It is to a certain extent, but the type of humor Mrs. Maisel is attempting to do is part Lenny Bruce and a bigger part Rusty Warren (and possibly a touch of Belle Barth, also in this archive).
I have gone through the jazz, classical and folk, too, and am again amazed at what is supposed to be in the public domain. I also found an error in dating for the Chad Mitchell Trio's 1965 release, That's the Way It's Gonna Be. The archive has it listed as released in 1960. That is wrong, and they should have been able to notice the Phil Ochs song that was the title track on the album was not yet written at the time, and neither was Dylan's Mr. Tamborine Man, which is also on the album. Still, this is an amazing project and one that is hopefully being supported.
The key, however, are the classical pieces in the public domain. Awesome stuff, including Ralph Vaughan Williams symphonies and other composition.