Any of you who have ever discussed copyright, public domain and fair use know that the conversations can quickly become heated and distraught, culminating in people attacking each other with Shakespearian insults, rotten bananas and copies of AACR2. My particular gripe is with people who discover songs they did not write and then copyright the songs in their own names. While the primary purpose of copyright law is more to promote and share knowledge than it is to protect the interests of the people who created their various works, copyrighting someone else's work (even if the authorship is unknown) seems dangerously close to plagarism.
At this time, songs that are published before 1923 are in the Public Domain-- that is, anyone can perform and record them. There may be particular versions of these songs that someone has copyrighted, and it's pretty easy to change a chord or phrase, then claim it as your own arrangement. Some songs have managed to have their copyright extended. I won't belabor the Happy Birthday issue again, but you can read about it in an earlier post here: Happy Birthday to--whoops!
While not definitive, here are some sources to help you determine whether or not the songs you want to perform are in the Public Domain:
Public Domain Music
MusicEase Traditional Songbook for Children and Adults
If you spot inconsistencies or things that are just plain wrong, let me know in the comments. I've already found one: in a couple of these lists, "All the Pretty Little Horses" is cited as a public domain song. In contrast, my Rise Up Singing book says that the copyright is 1934, renewed in 1962 and collected by John and Alan Lomax. However, it also says "International copyright secured" when there's no such thing as an international copyright.
Have your eyes begun to glaze over yet?
Update: One story of many demonstrating how copyright and public domain laws do not add up to an exact science: JibJab Media, Inc. v. Ludlow Music, Inc.