My "calloused skin" problem may be due to the way I hold the concertina, and it seems to be worse when I play music written in the key of Bflat -- I think because so many notes are on the "pull."
As I hang onto the concertina, it seems some of its weight is handled by my right thumb, near the joint.
As it rubs against the metal bracket loop that holds the strap, it creates a calloused condition.
My wife wrapped some thin yarn around the metal loops, but it keeps moving. As long as it is in place, it seems to help the situation.
I was wondering if anyone else has this problem (misery loves company) and if anyone has come up with a good way to pad that metal loop (why reinvent the wheel?).
Ideas appreciated.