I can play mouth organ, tin whistle and, occasionally with simple tunes, anglo concertina by ear. I am talking about a piano accordion in this case and I am still learning so need to know what the chords are. I find the sheet music the best way for that as if I was doing the chords by ear I would probably stick to G, C and D for this. Looking at the music you find a couple of E minors and A minors. My ear is not good enough to pick those out so, sorry Steve, if that makes me bad person, so be it ;-)

DtG