pitch raise Sequence and viscoelasticity of wood(Re: Different Pitch Raising Sequence)

[baoli liu]

> I pitch raise starting in the middle of the piano,
> and go up, and then down. 
> I have found the piano to be more stable in the long
> run, than if I did it 
> according the directions. Although Dr. Sanderson has
> stated it doesn't make 
> any difference, I am more comfortable with this
> method, and think it does 
> make a difference. 
> 
> Willem 



In my opinion,pitch raise sequence has influence on
the results of piano tuning,especially on the
stabilities.

As I said before on the list,different section needs
different amount of pitch raise--take an upright piano
for example,the lowest bass string and lowest tenor
string needs less pitch,one main reason for this is
that the(section of) bridge for these notes is located
on the edge of the soundboard,when the soundboard is
depressed by the adding force of pitch raising,the
edge of soundboard,as well as the edge of the bridge
moves less than that of the center.

Other section of the scale may need more pitch
raise.the high treble section needs more pitch
also,because the string stretch,or more exactally,the
string movement from unspeaking length to speaking
length.

So when pitch raising by ear,one should tune the "more
pitch raise section" first,and then tune the lowest
bass note and lowest tenor note at the end.
When pitch raising by SAT or RCT,the sequence should
be opsite from that aural pitch raise(or one can also
set different percent pitch raise to get the best
results).

Because the wood has the characteristics of
viscoelasticity(different from the characteristics of
elasticity),that means the shape change of the wood is
not only a function of force which is added to a wood
structure like a soundboard or pinblock,but also a
function of time.So pitch raise sequence does has
influence on tuning results,especially on long run
stabilities.

I'd be glad to know your comments and corrections.

Baoli Liu
School of Music,University of Wisconsin-Madison


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