Seasonal pitch change:

[Ron Nossaman]

> Could it be because that's where the strings end? You have an abrupt 
> loss of downward force on the bridge/soundboard, plus (if I understand 
> what the Rons and Del are saying), those strings tend to have less 
> tension due to poor scale design. 

Low break%. A string at 20% of break tension changes pitch 
much more with a given length/tension change than one at 40% 
of break tension. The reason those low tenor notes are so 
touchy to get in tune is the same reason they change so soon 
and so much when they go out.


>I think Ron N was saying some days ago 
> that his redesigns are not nearly as susceptible to pitch change as the 
> original scale was.

The two primary reasons for that are the laminated bridge caps 
and string scaling. Tuning differences at scale breaks are 
minimized by the scaling, and overall pitch stability 
improvement is from the laminated caps. One tech described it 
by saying the piano can drift further off pitch without 
sounding out of tune than other pianos. Yes, they do go out of 
tune, but they do so much more evenly than we're used to 
hearing, and not as far as we're also used to hearing.


> The strings adjacent the plate struts are more prone to change during 
> tuning. Gotta be something to do with the lack of tension on those 
> portions of the bridge at the ends of a section of strings.
> 
> JF

Correct. Log length progression compromises from lack of 
sufficient dogleg at the strut makes a discontinuity in break% 
there too. The F-5, I think it is, in the Yamaha P22 is a 
classic example. The first note above the strut, and it's 
always WAY off from everything on either side. Ok, F# too, but 
not as bad.
Ron N