Capo noise, where it comes from

[Ron Torrella]

On Tue, 15 Nov 1994, Michael Wathen 556-9565 wrote:

> I'm not sure who wrote this because they didn't sign their name and the
> software they use here will not allow me to see the individual's name,
> only Pianotech.

Michael,

This was written by Bill Spurlock....

>> I think Michael has pointed out that there is more to clean treble sound
>> than just the shape of the capo bar. I too have had pianos that continued
>> to zing after a "proper" shaping, even after string leveling, reshaping,
>> and checking string deflection angles. I suspect capo bar smoothness is
>> very important, but other factors include updraft angle, string tension,
>> length of front duplex wire and diameter of wire, hammer hardness, as well
>> as profile of the capo.
>>
>> Like Ron, I too have had the experience of eliminating string noise in
>> the capo section by resorting to hammer voicing after all capo remedies
>> failed. I felt like I was treating the symptoms instead of the problem
>> by needling the hammers, since I could stop the noise by touching the
>> front duplex section with a finger.
>>
>> However, some deep shoulder needling stopped it without appreciably
>> changing the tone.

> My point seems to be missed.  The question is where does the noise come
> from?  My belief is that it comes from the capo bar and that it is a
> symptom of a larger problem that needs to be "dressed".  Yes, you may
> get rid of the noise by voicing.  Yes, it may appear that it has not
> seriously affected the tone.  But, due to the reasons that I outlined in
> my first post on this subject I'm willing to bet that were you to
> measure the difference you would in fact find a discernible change.

I noticed *no* change after dressing the capo bar until after I voiced
the hammer.  The offending zing before restringing/redressing remained.
The question of whether or not the *tone* changed is irrelevant to the
question of what causes/-ed the zing.  (Yes, the tone changed a bit.  No,
the zing remained.)

> Next, I feel that perhaps the most important aspect of this discussion
> is the fact that there are to normal modes of vibration for the string,
> one horizontal and the other vertical (Weinreich, Journal of Acoustical
> Society of America, August 1977).  Our proof of this and the fact that it
> is a significant factor for technicians is directly observable on a single
> string that is not correctly seated on the bridge.  In this case the
> string supports [two] different frequencies because the horizontal length
> terminates at the bridge pin while the vertical length terminates
> somewhere behind the bridge pin on the bridge.  If we have a problem with
> this case due to this existence of the horizontal motion of the string
> then we should expect a problem with this same motion at the capo bar. The
> capo bar needs to reflect the energy efficiently in the horizontal
> direction or there will be a great energy lose at the capo bar as kinetic
> friction.

If this is the case, then why don't we have ribbed capo bars to prevent
horizontal movement at the bar (along the lines of the rationale behind
tipping the bridgepins)?  Further, how do you explain the apparent
elimination of the zing after voicing?  A different attack on the
string?  A different velocity somehow?

Ron Torrella                  "Dese are de conditions dat prevail."
School of Music                           --Jimmy Durante
University of Illinois