As I said: I'm sure other players will explain this much better than me- and far more correctly! Just trying to make it clear (and not very well) that the "duets" Al and I play are not "duet" concertinas but musical duets.

I've been interested to see, on my own forum, that most of the members - being mainly guitar players and mainly American - were not really au fait with the concertina, and certainly not aware of the different systems. So I was being a bit pedantic - and inaccurate!