WAV.
You've played nicely(?) into my hands.
I play McCann Duet concertina.
The whole point of this instrument is to accompany oneself.
(Imagine a Harmonium in a box)
If I were you, I'd check out, Alexander Prince, Iris Bishop, Gavin Atkin, Michael Hebbert, Peter Honri.
When you have discovered these amazing musicians, Then get back to me.
Alistair Anderson plays the English system (Jolly well), but, the English doesn't lend itself, easily, to harmony playing (well it does, but you've got to be very good to make it work!)
You obviously don't have the faintest idea of the differences between the systems.
Go Study.