From Mike Harding: On the recording, 'Soon May The Wellerman Come' was sung by Tommy Wood. In response to the world-wide interest and in preparation for a radio programme on New Zealand folk I contacted Tommy. From the source....

Thank you for this! If nothing else, it explains the curiosity that the tune on the recording does not match the tune in Song of a Young Country: Wood and Colquhoun started with a sketch of a tune, but Wood made it major and Colquhoun Dorian.

I'd looked casually for books on New Zealand whaling, but shipping made it prohibitive for books I'd be buying on speculation. Now I may have to try harder. :-)