I believe if a song is trad it is trad. The primary source didn't
pay for it, and should not be paid for it.

On the other hand, the collector should be paid for his LABOR, not
for the 'creatives' on the song. That means no royalties, no
copyright. Maybe 'copyleft' which puts it in the public domain
with no royalties. So you got paid in 1966 for collecting a song
and for transcribing it, and for putting it in a book and selling
the book. But you don't get paid every time someone performs
the song at a gig or puts it on a record. That's stealing from
the tradition.

And no fair collecting from a primary source and applying music
theory 1A to figure out that the chords are G, C, and D, either,
or putting dots on a page, and claiming copyright, either.

As a collector who doesn't pay primary sources, you get to claim
copyright on the BOOK that you put the song in, on xerographic
copies of the pages themselves, and THAT IS IT.

On the other hand, the collector who does the 'adapted and
arranged by' thing willy-nilly OUGHT to be paying his primary
sources and their descendants, for the prescribed period of
copyright.