Tuning double octaves bass side

[Pierre]

Hello,
While tuning the left hand double bass reeds I noticed an unstable pitch in the lowest notes ; a swing from about -3 cent to +4 cent so the double octaves are a little false when the note is attacked until the pitch stabilises and sounds in tune. My tuning target was slightly above pitch (after the attack) but now I think I should tune these lowest notes even higher to have a cleaner starting pitch. Does this make sense?
Maybe the (new) leathers are also interfering but I took great care when replacing them even if some are stiffer than others.
Pierre

 

[debra]

It is normal for the lowest notes to take a bit of time to reach a stable pitch, and that pitch may also be volume-dependent. So that's bad news, but the good news is that a small deviation of 3 or 4 cents in these very low notes is hardly noticeable. I prefer to tune to 0 cents at a reasonable volume level (mezzo forte), so at fortissimo the note will be a bit low and at pianissimo it may be a bit high, but none of this should be noticeable.
All this is assuming that your low notes are indeed really low notes. (On some smaller accordions the lowest bass notes are not really low.)
A deviation of 1 cent is 1% of the difference between a note and the next half-tone up. When the note is around 50 Hz the next one up may be around 54 Hz so 1 cent is 0.04Hz meaning that your deviation of 3 to 4 cents is something like 0.15 Hz or one beat per 7 seconds. This is not going to be noticeable. If you do hear the low notes are out of tune the deviation must be much larger.
Note that at these very low frequencies it also takes a little bit of time for a tuning device to pick up the precise frequency.

 

[Pierre]

Thanks for your help Debra
Maybe there are other factors involved if some octaves doesn’t sound in tune when taking in account the slightly unstable lowest notes?

I am quite confident in the readings of my (very reactive) tuner but indeed some double bas octaves are sounding more out of tune than others even if the readings are ok (I tune with the complete accordion with the keyboard upside down on a stand)

I suppose ideally double octaves would have to be tuned by ear using the high octave (more stable) as reference but it is not always easy to hear in which direction the correction should be done.
The accordion already sounds much better but I really would like to get close to a very good tuning. I suppose the weather conditions are also important and these days it is very unstable.
I noticed also that the accordion sounds better the day after the tuning job.
Pierre