Hi, Jo-
It's not a bad idea to post a list of songs you're considering in a thread like this one, and ask us. Our collective perspective is better than most resources you can find.

I'm sure you don't mean to say you thought all the songs in Rise Up Singing are in the public domain. "RUS" isn't perfect, but it does give fairly reliable copyright information (and most of the songs in "RUS" are recent and are still under copyright). There are differences in the rules from one country to the next, but I think that in general, you're safe thinking anything published in 1923 and earlier, is in the publich domain.

And, as an aside, we can give you proof (click) that almost every single song copyrighted by the Carter Family, is in the public domain - most Carter Family songs came from sources prior to 1923, even though the Carter copyrights are more recent.

-Joe-