Sketchy is right Will ;-)

The drones are not keyed and are just drones (same note in three octaves) the regulators are the keyed bits. When you hit more tha none key you play chords but when hitting one, and if you have a hand free, you can play al sorts of things. Limited but still.

Try look up Leo Rowsome playing The Castle of Dromore (or Tommy Kearney or Geoff Wooff playing same).

The arrangements in the collection you mentioned were for the piano forte though.