Thanks May!
I try to help where I can. May hasn't been in touch about playing before, but today she was working on one of my instructional YouTubes and asked how and why I was pulling a note on the G row while playing Harlequin Air in D. See
https://www.youtube.com/watch?v=Pd9MYjQUAMMIt occurs to me that some other folks, particularly beginners and improvers might be interested in the same question.
In the A music there's a A note. One could play it on the push on the D row - but that's dull and a bit shapeless... So here I pull the A on the G row, which enables me to play it against the A chord.
I suggest that when you play the 5th note in the scale, consider whether it should be against the key chord (D, in D) or it's 5th chord (A in D). Ditto in G: should the D be against the G chord or a D chord? Being able to do this is a key benefit of the two row compared to a one row.
It's really not an obvious thing and there are a great many folks happily playing two row melodeons as if they were two one rows in a single box. But it's a nice thing to be able to do, and obviously something you're more likely to spot if like me you come from a more chordy instrument, such as guitar or duet concertina!
I hope that helps, Gavin