I have call to play "The Hansome Ploughboy" in Am. Music also suggests use of Dm chords in B part. I suspect this means tune is modal.
The defining chord of western 'modal' minors is V .. in this case Em. Tonal minors (viz harmonic) have an E7 there (which melodeonists fudge by playing E major
I tried to google this tune to see if it has a sharp 6th or not (F#/F). That would make it Dorian, best played mostly on on a G row and harmonised by the 'G' chords. If the F is natural, it is simple Aolian minor - you'd should base play on your C row and use the 'C' chords (as available on your kit).
SURPRISE : *All the ones google found for me are in A major
Please advise. dots would help but a recording or video would be enough
See others had same luck. -- and 'Hansome'
met the same fate