Hi Chris!
you may have seen my comments on another post elsewhere on this new fangled forum (NFF) about chamber influences.
I am unsure just how the chamber design works, I have seen opinions along the lines that its absoluely critical, C. W. applied himself to masses of research on the topic, so it must be. The best concertinas had/ have stopped off chambers to improve performance so it must be true. Chamber tuning, combined with long series reeds defined the orinal aelos c.f. the bog standard concertina................
What is true is that, once mounted in the chamber the pitch of a reed changes by a few cents (compared with being sounded in free air), and the tone it produces is improved. Something is happening.
Other opinions seem to run along the lines of: zero real influence at one extreme, to the chamber only influences reed starting speed.
I looked at the mathematics to see if I could find any correlations, but is the chamber comparable to an open tube or a closed tube? A bit of both, with the pad opening at one end and the signal generator at the other, but both on the side of the tube wall, and both part way down the chamber length. In the case of the reed (signal generator), often in the middle of the tube length. The best way to visualise what is happening is to look at th big reed instruments (sorry to be a bore on this topic, but its only a passing phase, I will grow out of it when I move out of the male meopause).
I say big reeds because the chambers are so much bigger relative to the reeds, see the photos of the Lachenal bass you once displayed for me, and of the damaged chambers on the 'Big Reed Performance' posying on this NFF.
On the basis of observation, I believe that the chambers do influence harmonics, as much as primary frequency projection, but that their design is not so critical.
My basis for this is:
Big bass, I have found evidence of reeds being moved to standardise the fingering from some form of obscure brass band equivalent transposed fingering, this does not appear to have affected reed performance
Anglophiles change the pitch (key) of instruments by moving reeds around
On repairs/ service jobs I have inserted false end walls into chambers, to try to smooth out unpleasant harmonics, sometimes with success.
As usual, no hard facts, and a lot of semi-educated guesswork, what my Professor used to call SWAG, Sophisticated Wild-Assed Guessing.
Dave