[pianotech] phenomana - Another ETD Check

[Ron Nossaman]

On 5/14/2012 11:38 PM, Joseph Garrett wrote:
> Ron said:
> "Hmmm... On second thought this could also be interesting to see how the
> individual note numbers of even one piano differed from one ETD tuning
> to the next at a 30% or more RH% difference. Any chance?"
>
> Ron,
> I have a sneaking hunch what you are alluding to.<G>  I have observed, on
> some of my 3-4 times a year, pickyuny clients, good pianos, a strange
> thang. Since I passed my RPT, aurally and now use a SATII, this phenomonon
> has cropped up many times. Although, I do not use recorded tunings w/the
> SAT, I do pay attention to the "stretch factor" on each tuning. On the same
> piano, but different times of the year, w/different humidities, I've
> noticed that the "Stretch Factor" numbers are different. Example: On one
> tuning the SF will be 1.2cents on A4, with the machine set at A5. The next
> time, the darned thing will yield a SF of 2.4 cents. Same piano, just
> different humidity. I keep record of the temperature/humidity every time I
> tune, so I have references to check. It is my thought/guess/idea/whatever,
> that the moisture content in the sounding body will create different
> inharmonicities in relation to the moisture content of the wood, (in
> relation to the given differences in humidity.) I have no way to verify
> this, but it's been the reason that caused me to question the validity of
> "stored tunings" and to come up with a method that works for me,
> tuning-wise. (refer to my PTJ article, January 2000. (I'm constantly
> upgrading and refining that method, but, it works for me...most of the
> time.<G>)
> Regards,
> Joe


Hi Joe,
I'm not alluding to anything concerning ETD use. I don't use an ETD for 
tuning, so I have no interest in the tips, tricks, tweaks, and 
workarounds concerning them. What I'm interested in here is how the 
finished tuning of the piano differs under different humidity 
conditions, and how the tuning, arrived at by an aural master tuning by 
committee, or a more mainstream tuning, on the same piano by the same 
means compares - by the recording using an ETD after tuning - with the 
tuning of the same piano done by the same means at a significantly 
different humidity level. I'm looking to learn something fundamentally 
useful here that I've never seen addressed before, and since I neither 
use an ETD, nor serve on a tuning test committee, I'm asking for help 
from someone who does to indulge me in some basic research. FAC numbers 
don't help, nor do descriptions of process. What I need are finished 
tuning note by note frequency measurements (or equivalent cents offset 
from a non-moving "standard" frequency) from each piano at each tuning. 
I want to see how both an aural super tuning, and a saved ETD tuning 
reproduces at, say, 30% and 60% RH. This is an attempt to learn 
something about how pianos work, not about how ETDs work.

Ron N