Chas,
Sometimes a sudden improvement in ability just leaps out unbidden. Years ago, when I'd only been playing Anglo for a couple of years or so (but not being able to sing with it) I took up 'spoon bass' melodeon. After about a year I was frustrated that, although I could do reasonable chords with the left hand while playing most songs and even dance tunes when playing Anglo, doing anything at all with the simpler two-spoon bass on the melodeon seemed beyond me, completely.

Then, after being in Canberra one weekend for the monthly Yarralumla Woolshed dance (calling and playing mostly lagerphone) I had to hightail it, on the Sunday, all the way to the Grampians to be part of a school camp by early Monday morning. I arrived in the middle of the night, dog tired, pitched tent, and arose at dawn with a tune in my head that I'd never known before and a need to get it down to my fingers. It struck me as perfect for the melodeon so I pulled that out (instead of the leather ferret), sat on a stump in the rising sun, and started playing.

Unbidden, the tune came straight out of the fingers of both hands at the same time and I've never looked back. It was years later that I found out the tune was to the song "The rabbit trapper". There had been a session at Mike Jackson's (where I and others in Higgins MMB and Dave de Hugard were staying) after the dance and Dave had been playing it, or so I worked years later. Something about being tired at the same time as being inspired with trying a new tune must have played into my hands.

Singing came along in much the same way; "Two little girls in Blue" on the Anglo came first as I recall (I think it no accident that it was a waltz tune) and "Travelling down the Castlereagh" not long afterwards on the melodeon.

Best of luck!

Cheers, Rowan