I happen to have a couple of PP&M songbooks from days when I started playing and singing way back when. According to them, the answer to your question is that the copyright owner for A'Soalin' is PEPAMAR MUSIC CORP. in 1963 & 1967. The books say by (or words and music by) Paul Stookey, Tracy Batteast and Elena Mezzetti.

Those are the facts from the books. My opinion is that PEPAMAR is an acronym for Peter, Paul & Mary. I believe that the various songs that make up the song are in the public domain, but that the particular arrangement you asked about is their copyright. Hope this helps some. I don't recall seeing anything about PEPAMAR at the PP&M web site, but you can e-mail a question about it from there if you need to know more about using that copyrighted version of the song. Their site is http://www.downeast.net/ppm/ if you don't have that marked.

Allinkausay,
Bill