Soundboard Deflection and Pitch Change / was Downbearing

[John Delacour]

At 9:12 am +0200 18/8/06, Ric Brekne wrote:

>..why then does the lower end of the treble behave so differently 
>then the upper end of the tenor.. and likewise with the lower end of 
>the tenor vs upper end of the bass.

Because the tension of the strings is commonly nearest the breaking 
strain in the high singles and the high bichords and furthest from 
the breaking strain in the plain wire strings to the right of the 
break.  The shorter the piano the more these differences are likely 
to be unavoidable and significant.  A string that is at a tension 
well below the maximum (eg. 130lbs. on a #20 wire, as you might 
easily come across on an upright or a less-than-6ft grand) will be 
far more susceptible to changes in humidity and temperature.  Where 
do you get the most fluctuation in pitch on the 5ft grands you tune? 
Almost certainly in the plain wire notes to the right of the break.

JD