I believe this is the tutor that Inventor is referrring to: http://www.concertin...kshop-Tutor.pdf
I wrote a beginners tutor for the Hayden concertina, which gives a very simple bass line for the left hand side. Included in it is "The High Barbary" one of the sea songs that Bob Roberts of Penmill used to sing along with many of his sea shanties.
This gives a simple counter melody to the tune. However for sea shanties I would personally suggest a good rhythmic um-pah bass to get the anchor up and the sails hoisted might be more suitable.
You will find the above mentioned tutor on the other concertina site (concertina.com).
If you have any other questions about Hayden concertinas you should post on the teaching and learning section of this web site.