Part of the problem is that a lot of those songs aren't so melodic, so the melody part might sound a bit monotonous on concertina.
And not monotonous on other instruments (including voice)?
Wouldn't that be part of the genre?
That said, the easiest chords are I-V chords (neither major nor minor),....
...5 chords ("power chords", though that's not what we call them on Appalachian dulcimer...).
Not what I call them, either. In fact, I've never before encountered the term. I wonder who made it up, and when?
In my understanding, a "chord" contains at least three
distinct notes. With only two notes, it's an "interval".
Intro: F#5 E5 F#5 A5 E5
Verses: D5 A5 C5 B5
The "5" just means to play only the root and fifth, so D5 is just a D and a A.
Same with that notation. Completely new to me. To me, it's not a "5 chord", but just a "fifth".
And while I personally like open fifths and use them a lot, I don't think that they deserve a name that suggests they're more "power"-full than real
chords which have 3, 4, or more notes at once.