Wow, another owner of the 67-key square Hayden! I bought one from Brian last October, shipped across The Pond, and a new member here named Grant has been playing one too. That makes three of us on this board.
This sudden burst of interest in the Hayden duet is of great interest to me as I have just bought one of the square "bandonion" models.
Don't know if it's much practical help, but have you seen my thread under "Instrument Construction and Repair" where I give a photo tour of the 67's inside and out? This will save you from taking yours apart to admire the fine construction of the reed banks.
Any guidance on playing it, helpful web resources etc, received with gratitude (and maybe even thanks).
Actually, it's safe to take an end off and access the reeds. Taking the action cover off will leave you with a real challenge to get all the buttons back thru the felt-bushed holes -- so look at my photos instead
PLAYING -- the handle/strap setup tends to tilt your finger downward across the rows, so your index finger hits high and your pinky misses low. Try to keep your thumb pulled back on the hand rest, so your wrist enters the strap at an angle from below, not above.
You may find some of the reeds sluggish, and unevenly voiced, so you have to play fairly loud, squeezing hard, and the bellows don't hold a lot of air so you reverse often.
But man, do those LH side deep bass chords sound fine! Move over, Stradella!
Brian and I had quite a bit of chat before closing the deal, Halfway thru I finally realized who I was talking with!
I am in touch with Brian since I bought it from him,
ANywa, ROger, welcome to The 67 Club! --Mike K.