Willy Moore is pretty much a three chord trick, whenever I've heard it. That sort of appalachian banjo sound. I can't bring to mind Joan's version.

her version of Come all ye fair and tender maidens is pretty simple.

it revolves round playing the C to A minor rundown, followed by the G to Eminor

so play the d7 trick mentioned in previous post.

Come all you fair
and on the word 'fair', you play middle C - that is 5th string fretted at the third, then in rapid succession 2nd fret of the 5th string, then 5th string open - moving from a C chord to a A minor.

Then Take warning how, and on the word 'how'

you hit G - That is 3rd fret 6th string, then in rapid succession 2nd fret 6th string, then sixth string open, - moving from G chord to Em chord.

Hope this is clear - its easier to show you than write it down. I bet theres some people round your local folk club who can demonstrate.
Joan probably capos three - to make the song in B flat
all the best

al