[CAUT] pre-stretching new string?

[John Delacour]

At 12:00 pm +0100 10/6/07, Richard Brekne wrote:

>...If you actually apply this formula find out what kinds of things 
>need to happen to a given string for it to experience the kind of 
>pitch changes we observe... you immediately see that the pitch 
>changes we see at the tenor bridge have no (at present) good 
>explanation.

What objection do you have to Wolfenden's explanation below?

JD

At 7:47 pm +0100 27/4/07, John Delacour wrote on this list:

>The most succinct description I know of of this phenomenon comes from
>Wolfenden, writing in 1916.
>
>_____________________________
>
>         It is now known from experience that practical equality of tension
>      throughout the instrument tends to prevent changes in the tuning due
>      to variations in the temperature.  When the tension is equal the
>      temperature movements are equal.
>         In former days pianofortes were exceedingly sensitive to changes
>      of temperature, mainly because the fact noted above was unrecognized
>      or disregarded.
>         A thermometric movement of a few degrees often sufficed to render
>      (in a very short time) an instrument unusable, and had the tuner
>      recently paid one of his visits, the discredit of the change was
>      charged to him.
>         The notes in which the greatest changes occurred, were the lower
>      ones which were strung with plain steel wire.
>         I have known numerous instances in which the changes in these notes
>      were equal to nearly a semitone between midsummer and midwinter,
>      while the other parts were relatively stable.
>         This was due to the customary very low tension of these notes.
>         There seems to be a point in an ascending scale of tension, at
>      which the elasticity of the wire is almost suddenly developed (*) to
>      an extent we could not anticipate, so that a difference, so that a
>      difference, which would be very serious at a general low tension,
>      will become more tolerable.
>         To make this intelligible, let us suppose an instrument in the
>      tension of pitch C is 130 lbs., and that of C two octaves lower is
>      only 100 lbs.  This piano will be extremely sensitive.
>         But let us now suppose that we can lift the tension so that pitch C
>      stands at 200 lbs. and the other at 154 lbs.  While there still
>      remains a liability to change, it is much reduced, although the ratio
>      of the difference in unaltered.  Covered bass strings, which are