Irish concertina players usually use a cross-the-rows fingering which works out smoother for reel playing. That's been one of the big changes over the last 40 or 50 years- English melodeon players developed a cross fingering that transformed the instrument from the humpty-dumpty jerky sound to a smooth flow. Irish players use(d?) either BC or CC# boxes, which give a smooth tune line but never had any chords that worked. I suppose that fits better with Irish dancing, at least one hand does nothing. Jimmy Shand apparently had a special three- row box made, CC#D I think, with a piano- accordion left end so more chords than soft Mick.