Humidity Change and Unisons

[Ron Nossaman]

>More items for the list. I think you mean Occams rasor. *smile*.

Hi Don, I do indeed.


>How does one measure the tension in the tail length or the front segement?
>Are there formulas for these numbers? 

I don't have a clue. I suppose I'd try plucking the segment, measuring the
produced pitch with a magnetic pickup and/or ETD (whatever proves to work,
I haven't tried it), and calculating tension from pitch, segment length,
and wire diameter with the usual scaling formulas. I expect it would only
be a coarse estimate at best, but it could be a good indicator of
principals involved, if not absolute values. 



> I wonder if deliberately trying to
>leave extra tension in the front lenght on the bass side and deliberately
>leaving lower tension on the treble side might ameliorate the smearing.

I doubt it. So much depends on not only which direction the humidity swing
was going when you last tuned, which direction it's going when you tune
this time, and the direction(s), amplitude(s), and number of iterations it
will go through before you see it again. You can't know exactly where the
back scale tension is when you finish tuning a string, so you can't
realistically predict exactly where the tuning will go next week, next
month, etc. It's a design and climate control issue , not a tuning one, and
tuners are already crazy enough without tilting at this particular
windmill. I suspect that designers generally don't lose too much sleep over
this either, though one we know is careful with active back scale lengths
and such. From a field service standpoint, it's what we have to work with,
each piano is unique in all the world as to how, exactly, it will react to
humidity swings, and there are WAY too many of them in line behind this one
for service to get too deeply into second guessing the minutiae. Just
because you can explain why it happens don't mean you can fix it. 


>Another point if the results are consistant, then some time can be saved
>because one knows what to expect of the unisons as a rule of thumb.

Does one? Only after verifying which direction this smear occurs. My whole
point is that I doubt there is a reliable rule of thumb. We "play it where
it lies", so to speak, and press on.



>I don't think that when one is following one's own tuning it can be...a
>rumor LOL!

Not so, sir! Haven't you at some time followed your own tuning and found
odd glitches in the old tuning that shouldn't be there, and that you can't
explain? I sure have (that's with my tunings, not yours<G>), and can't help
but think - did I screw something up then, or am I screwing something up
now? There's always some degree of FUD involved when we're dealing with
anomalies.  


Ron N