I'm curious about something in the tuning graph. I'm learning about tuning so I'm not sure if this is obvious or not. The deviations of the three reeds seem to be somewhat correlated. That is, if I look at a particular note on one reed and it's lower than where the interpolated line would be, the corresponding note on the other reeds seems likely to be low as well. Why might that be?
Edit: Just realized this conversation is two years old. I thought it was from a few days ago! Please excuse the dredging.
No problem reviving an old thread rather than starting a new one on the same subject.
First let's look at the standard reeds (not tremolo). In my experience a tolerance/deviation of up to 1 cent is acceptable around the A4 note, going down to about 0,5 cents at A5 and higher. That is quite critical tuning. Others will probably say 2 cents at A4 and 1 cent at A5 and higher. What is most important for LMH tuning is that I should not be able to hear any beating at all when playing an octave using LMH, that means that 6 reeds are playing simultaneously. (Note I said "I should not be able to hear..." and not "you should not be able to hear...".) I have been "accused" of being too critical, but it's best if the tuner is the most critical, not the customer.
As for the tremolo, the player has to chose an amount of tremolo for A4. The example graph shows +20 and -20, which was quite common 50 years ago, but nowadays +10 and -10 or +12 and -12 at most would be more common, and in an LMMH or LMM accordion the MM can be 0 versus +14 (German) or +16 (Italian) tuning. Amsterdam or Irish tuning is more like -25, 0, +25 and I think it sounds horrible.
Once an amount is chosen, say T, the tremolo goes up as you go down the scales to a maximum of about 1.3T down to A3, and no more than that as you go further down. Going up you reduce the tremolo from T at A4 to about 2/3 of T by A5 and again about 2/3 of that (4/9 of T) by A6. As an example, when T is 12 cents, the tremolo at A5 should be about 8 cents and at A6 about 5,5 cents. The desired amount of tremolo for the highest notes is pretty much a matter of personal taste. You should consider that when the high reeds are tuned to within 0,5 cents that can result in still too much variation of the tremolo on the high notes. Even when one reed is exactly at 0 and the other is 5, 5,5 or 6 cents you will clearly hear the difference in beating, so it is very, very critical. The table shown by the OP is of an accordion that is seriously out of tune!