When a work is published more than one type of copyright can exist. For instance it may be permissible to copy a text by hand because the content is public domain, but not to photocopy the actual printed page because the layout, typesetting etc. are the copyright work of the publisher.

Or a collection copyright may exist where a substantial amount of work has been done in assembling a list or anthology of works to which nobody owned individual copyright.

The Performing Right Society allows performers to register and claim performance royalties for their own arrangements of traditional songs. This was introduced a few years ago, though I'm not sure that many trad performers take advantage of it. I think that process regards the performer as owning copyright for the arrangement. Of course many songwriters are PRS members and have benefited in this way from performing their own songs.

The Carthy/Simon case was ususual because (a) a lot of money was at stake and (b) the arrangement had some very distinctive features that were quite clearly Martin's work. I don't know if Paul Simon was claiming copyright ownership, but he certainly wasn't paying Martin any royalties until the case was settled (amicably, out of court, as I understand it)

Anahata