Casottos and wider tunings

[Ganza]

This is a very subjective question, but does having the two M reeds tuned say 2-3Hz apart, with one M reed in casotto and another M reed out the casotto, sound good?

Or do usually those with an M reed in casotto tune the M reeds closer than 2Hz?

Because I know with most French accordions, they only have L and P reeds in casottos, not usually M reeds.

Is the reason for this that having one of the M reeds in casotto and one out changes the quality of the vibration?

 

[debra]

When one M reed is in cassotto and one M reed is not it is harder to have a nicely balanced tremolo sound than when both are outside of cassotto. But harder does not mean it cannot be done. For the amount of tremolo it makes little difference. If anything the tremolo may sound a bit better when there is a bit more tremolo with the in-out configuration than with the out-out configuration.
WHen two M reeds are tuned 3 Hz apart that is 12 cents and is actually a rather light tremolo. 4 Hz is a more "real" tremolo and is 16 cents. Small differences from one note to the next are also more noticeable with light tremolo than with a stronger tremolo.
It is all a matter of taste, not just the amount of tremolo for the standard A but also how it evolves towards lower and higher notes. Getting the tremolo exactly right to the wish of the customer is one of the most difficult tasks for an accordion tuner.