Soft blows

[Bill Ballard]

At 9:15 PM -0700 10/26/04, jason kanter wrote:
>I'm not assuming it, I agree the goal is for the test blow NOT to change the
>unison, but from the test blow's perpective it is intended to expose any
>instability that may lurk in the unison.

I think the question we're both pursuing here is whether a test blow, 
instead of just confirming the absence of instability, can actually 
alter the stability (leave the note less stable), without somehow at 
the same time, changing the actual tension inside the speaking 
length. I think you're asking the same question of Andre again 
further below.

>  > The "bump-up-bump-down" is what I trust.
>
>Can you say more about this?

When you think the pin and string are set, nudge the hammer CW and 
see how large a nudge it takes to produce a change in the speaking 
length. Nudge it CCW, looking for the same. If the nudge flat to 
overcome the friction barrier (capo/aggraphe plus rest felts) is the 
same as the nudge sharp, then the string's tension is in the middle 
of the zone in which the friction barrier is greater than tension 
differential on either side of the barrier, in fact equidistant from 
either "tipping point". Unless string or pin friction are out of the 
comfort zone, both string and pin will quickly return to their 
original position after these nudges. (In fact it may not be 
necessary to twist the pin anywhere near the break-free point.)

One can't be any more stable than dead smack in the middle of that zone.

>  > Ten years ago I measured the side view of note C5 on a Steinway Band
>>  the maximum vertical displacement on that note caused a hard blow,
>>  and fellow NH chapter member Doug Kirkwood and I calculated the
>>  string friction barrier at the capo and the momentary tension spike
>>  of a test blow. 21 lbs vs. 3.5 ounces respectively, as I remember.
>
>Sorry, I don't understand the experiment. Can you explain?

I measured how high the strike point of the string would jump up on a 
string blow (a maximum of 0.049", as I remember). I also measured the 
length of the string segments from tuning pin to the speaking length 
as well as their inclination (actually the height down from a 
standard line, of string path bends). This became a side view of the 
string path, from which to calculate the pressure against the capo 
and the front duplex, caused by the deflection that each of these 
created in the string path.

>Clarifying: I was asking the former, and I took Andre's answer to be a reply
>to the former. I don't think there is any argument that hard blows
>themselves produce tones that are less pleasant, have exaggerated upper
>partials, etc. I was asking whether the hard blow, used purely as a means of
>"proving" the stability of the unison, will damage the unison somehow, even
>if the unison is afterwards played softly and is found not to have moved.
>Andre seemed to say that yes, the hard staccato blow actually does damage to
>the unison. I'm still scratching my head.

What other ways are there to measure a unison (or a test blows effect 
on it) other than the presence of beat rates. Mind you, there are 
many who think that a beatless unison (when it does occur) is dry and 
lifeless, and benefits by a judicious amount of motion in the 
partials. I'd guess Andre is one.

At 9:29 PM +0200 10/26/04, antares wrote:
>The very hard staccato blow does damage the beauty of the unison.

At 7:36 PM +0200 10/26/04, antares wrote:
>The example I gave here of a technician working on a beautiful 
>concert grand, who made ugly (to my ears!) unisons, shows that 
>indeed your unison is not necessarily my unison.

That's all he wrote. Which is where words fail us, especially "text 
across the net". All of this would clear up quickly were we all 
sitting around one piano.