As usual on the web, nothing in this post is legal advice. Nothing in this post establishes a lawyer-client relationship. It is just private opinion. And I'm not even a lawyer.

There are a number of different practices that can be called "copyrighting a traditional song." The most egregious is when a publisher sticks a boilerplate copyright notice on purely pd material. In theory such copyright notices are pure bluff, but I don't blame anyone for shying away.

Then there is what is known as a compilation copyright. If I compile a book of pure p.d. songs, and publish them in pure p.d. versions, my "selection, coordination and arrangement" of songs, if it is original, is copyrightable. In practice I take this to mean that anyone can legally copy any single song from my songbook for any purpose; no one can legally copy my songbook cover-to-cover and sell it in a competing edition; and the coordinated copying of some of the songs but not all of them is a gray area which might be legal in come circumstances and not others.

Then there is derivative-work copyright. If I take a traditional melody (say, "Greensleeves") and change notes and rhythms to make a derived melody (call it "Greensleeves and Boston Cream Pies") then my copyright only applies to my original modifications to the underlying melody. In theory anyone can take my melody from my published edition and reverse engineer it to recover the original. In practice this is not always easy unless the copyist has independent knowledge of the original in the first place. I call this the "derivative work deconvolution problem." Reverse-engineering a derivative work would be much easier in situations where the p.d. component was intact and easily separable if arrangers would word their copyright notices precisely: "Harmony copyright 20xx by Joe Schmoe. The melody is in the public domain and may be copied freely." But this practice is rare.

Some of the publishing industry's overreaching practices are discussed in this law review article by Prof. Paul Heald, and in the article of which an abstract can be found here.

Sifting the copyrighted from the uncopyrighted components of derivative works would be easier if the term of copyright were shorter, since then the documentation of the P.D. components would be more readily available.

T.