[CAUT] jack repetition

[Fred Sturm]

Hi Jon,
	I'm going to disagree to some extent with what you write here,  
inserted below:
On Aug 11, 2007, at 11:42 PM, Jon Page wrote:

> For optimal action performance, the jack should move through as  
> short a distance as possible. This begins with key dip and action  
> ratio and ends with ultimately, the rep
> upstop and the jack pitch being sync'd such that the knuckle never/ 
> barely leaves the rep lever.
	I guess I agree that the jack should move as little as possible, but  
I would focus on the period of aftertouch, rather than the period  
while the jack top is scraping on the knuckle. That's where  
performance (repetition) is compromised. High speed video makes clear  
that the jack could get back under the knuckle in plenty of time if  
the darned knuckle would just get out of the way. It is amazing to  
see how many times the jack will bounce against the knuckle during  
very high speed repetition. I think the amplitude of those bounces is  
the major factor in how fast it can re-set (once the finger/key/wipp/ 
rep has reversed course far enough).
	 I am essentially in agreement that drop should be minimized. But  
not to nothing. There is a range where drop is disappearing  
altogether and the action can still function fine (with aftertouch in  
balance) that I believe "goes too far" from the point of view of touch.
>
> This places the jack at about half-core or forwards. A precarious  
> point which is on the verge of failure but at that 'racer's edge'.  
> All things considered, for a performance it
> might, hopefully squeak by but in real life we can't live on the  
> razor's edge and have to err on the side of sustainable performance.
	This is what several on this list consider to be optimal: as far  
forward as possible consistent with not failing (cheating out). I  
don't believe it is optimal. I don't think there is performance  
enhancement from this farthest possible forward position. From the  
performance point of view (actually getting the action through its  
cycle and re-setting to repeat), I believe the jack alignment is  
negotiable through a fairly broad range, without having _any_ effect  
on repetition (that is probably too absolute a statement, and I would  
love to see Stephen Birkett address the question  through high speed  
videography). It will, however, have a very noticeable affect on touch.
	And this is where I have been trying to focus attention. Jack  
alignment can be used to "fine tune" touch, in the sense of  
regulating feedback to the finger of what is happening in the action.  
And that feedback is very important to the pianist. I believe that a  
better default position for the jack is the conservative, "what  
everybody says officially" standard of lined up with the core. Not  
because it makes it less likely to have a cheating jack, but because  
it "feels better" to the pianist. That said, I also believe that  
there is room for fudging, both back and forward, to address the  
taste of the pianist.
>
> Regards,
>
> Jon Page

Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



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