[CAUT] pre-stretching new string?

[Michael Jorgensen]

REVELATION:
  We tune by listening only to the OUTPUT pitches of the soundboard
resulting from the INPUT forces of the strings.  If the INPUT of the strings
stays constant, but the board changed in stiffness due to humidity, the
OUTPUT pitches would be different with the same INPUT.  SO WE CHANGE THE
TENSION ON THE STRINGS OR THE INPUT TO GET WHAT WE WANT.  This would explain
how giant pitch swings can occur without any corresponding major change in
string length, tension, bridge position, or changes in crown.
  I doubt one could tune a piano by adjusting wire tensions to
pre-calculated theoretical amounts without listening to the pitches and
achieve any reasonable result.

-Mike Jorgensen----I'm outa here for a week now.

      

On 6/7/07 7:13 PM, "Ron Nossaman" <rnossaman at cox.net> wrote:

> 
>> Where the bridge pin ends up relative to the front
>> termination is an open question, not one easily measured.
> 
> Hi Fred,
> No, not easily measured.
> 
>> One of the 
>> Fandrich's (I forget which, but think Darrell) wrote about pitch change
>> due to elongation of the bridge toward the tenor end about ten years
>> ago, citing speaking length change as a major factor.
> 
> That was Darrell, and his premise was based on strings not
> rendering through the bridge. An interesting thought though.
> 
> 
>> Soundboard movement in response to humidity change isn't just up/down.
>> The position of the bridge relative to the front termination may change
>> due to whatever is happening to the board. A bit sideways, a bit back or
>> forth, a bit of change in cant. It certainly isn't as simple as up and
>> down, increasing/decreasing bearing (and, hence, distance from a to b,
>> and, hence, tension).
> 
> Nothing is simple or isolated, and this isn't a discussion on
> every potential detail of why and how pianos go out of tune,
> is it? My initial intention was to illustrate that string
> stretch wasn't the likely primary reason for long term pitch
> drop. I don't have authoritative details on everything that
> happens in soundboards with moisture changes, and most likely
> never will. I've picked up what I think are a few clues, and
> reported why I think so. That's the best I can do.
> 
> 
>> You really think the moisture transfer from the bottom of the soundboard
>> into (and from) the bridges of a grand is enough to stabilize the
>> bridges to a significant degree?
> 
> When it rains outside, the humidity level in my house
> increases even though the doors and windows are closed.
> Dampp-Chasers are least effective when the lid is always wide
> open, with no bottom cover, and most effective with a top and
> bottom cover.
> 
> Ron N