[CAUT] pre-stretching new string?

[David Love]

We're talking apples and oranges here.  Just do the math.  A string halved
which is at a particular tension is different than a change in length of a
string at a particular tension that results in a change in tension.  If you
have a string at 100 mms and stretch the string to 105 mms the tension will
change and with it the pitch.  That is a different thing than halving the
string at a certain tension which results in a doubling of the frequency at
which it vibrates.   

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of John
Delacour
Sent: Sunday, June 10, 2007 1:57 PM
To: College and University Technicians
Subject: Re: [CAUT] pre-stretching new string?

At 10:11 am -0700 10/6/07, David Love wrote:

>Sorry, but it's not quite a complete enough formula for purposes of 
>this discussion.  When comparing two strings that produce the same 
>pitch but with different tensions, either the original length will 
>be different or the diameter will be different (or both), thus a 
>similar change in length will yield a different change in tension 
>and thus pitch.

If this were so, then the whole basis upon which musical instruments 
are designed would crumble.  When you halve the length of a vibrating 
string, no matter how much strain is on it etc., you double the 
frequency, and if you stop two unison strings of identical length but 
of different mass, and thus tension, at the same point, you will make 
precisely the same change in their frequency and they will still 
sound in unison.  If this were not so it would be impossible to play 
a guitar in tune unless the tension of all six strings were identical.

According to Wolfenden, if the temperature changes, and one of the 
strings is well below its yield point whereas the second is close the 
yield point, then the strings will produce a beat because the less 
strained string is more sensitive to the change in temperature.  This 
is easy enough to verify by a simple experiment, which I shall do in 
the next few weeks once the new workshop is up and running.

JD