Jack, when you make a mistake, and someone points it out, it's rude to respond with:

"Ignored."   

For the record, I wasn't being pedantic... Robert Johnson was one of the people you mentioned, and his music, which is copyright in the US, will be under copyright longer than you thought. People shouldn't make the mistake of thinking it's PD, because Sony BMG Music owns this copyright, and you can bet they'll protect it.

By the way, Thomas Wolfe and King Oliver are also subject to this "pedantic exception," so three of your five examples won't in fact have their copyrights expire on Hogmanay.