Optimizing repetition (revisited)

[Jerry Anderson]

I'm sorry to come in late on this discussion of repetition
and jack position, but I was snowed under by work
as this interesting thread was being developed.

I feel that it is pertinent to mention that  any alteration
of the jack position vis-a-vis let-off necessarily implies a change
in the jack position when the key is in the rest position.

Our jack regulating method here in Paris, which conforms to Hamburg
procedures, is to regulate the jack, not in relation to the knuckle core,
but in relation to the angle the jack forms with the hammer shank.
This is in order  to maximize the amount of energy transferred to the hammer
shank from the pianist's finger in the first moment of key movement.

The principle is that the maximum amount of energy is transferred from
the key to the hammer shank when the jack is perpendicular to the
hammer shank at rest position.  If the jack is in any other position
the maximum energy transfer either peaks after the hammer has begun to
move (too late for maximum acceleration), or not at all (in the case where
the jack is regulated leaning slightly towards the hammer).

We do our jack regulating by lifting the neighbor hammers out of the way,
pushing the neighbor wippen gently to one side and sighting down the jack
to look for a 90 degree angle with the hammer shank.  Striking distance
and rep lever height have to be correct  to do this.

This is, of course, a description of an ideal situation.  Dozens of
variations in parts dimentions, rail positions,  wear, hammer boring,
etc., can and do necessitate compromises, and it is impossible to
ignore the jack's position in relation to the knuckle. There's always
room for a little tinkering, but we try for the most rapid response at the
beginning of key movement.

To develop what has already been discussed about repetition from the
bottom portion of key dip... if an action is regulated carefully and uniformly,
I believe that a first rate pianist can find a comfortable and rapid repetition
without letting the jack return completely to its rest position against the
spoon.
The essential is the uniformity of regulation so that the pianist feels the
minimum
risk in letting the key rise the minimum amount.  If this amount is uniform and
well defined, I believe the pianist will feel relatively at ease, even if
the piano is
not the fastest in the world.  Clearly, no two pianos will be alike in this
respect.
The various comments others have offered about drop, springs, key felt, and
lever position are all excellent and important.

We've talked a lot about the top action in regard to rapid repetition, but I
think
it bears mentioning (even if it seems obvious) that consistent repetition also
depends heavily on the stability of the action.  If the action starts bouncing
even slightly due to poorly set glider bolts, stripped out action bracket
screws,
cracked rails, or if the key returns to an inconsistent position due to deformed
key holes or worn key bushings,  the repetition will naturally become less
controllable and the pianist will glower.

Jerry Anderson


> With Alicia deLarrocha, the thing to notice is that she wants the
> repetition down at the ***bottom*** of the key travel.  She wants
it
> fast and she wants it consistent.  We have worked with her several
times
> and when she gets what she needs, the smile on her face is reward
> enough!

> See how genius can occur simultaneously in
>different locations?  Both are correct that the jack tail hits the let
>off button slightly earlier and the jack starts it movement slightly
>sooner.  In anticipation of everyone running out to the garage to delve
>into the mysteries of jack movement, I got out an action model.  I
>regulated the jack as normal, pressed the key and put a light pencil
>mark on the side of the repetition lever where the jack ended its
>travel.  Then I adjusted the jack _substantially_ back, away from the
>player.  Pressed the key and, as Ed and Jon theorized, the jack wound up
>at the same place, not as I thought, closer to the knuckle.  But I still
>think this works, only now I have to figure out why.  My thinking is
>that this gives the artist the feeling that there is more room at the
>"bottom" area of the key travel in which to work his/her repetition
>magic.  If you duplicate my experiment, do you think that a little more
>movement of the jack causes just a little more spring pressure on the
>jack down where that type of spring enters the jack, which may quicken
>the jack's return?

>Horace Greely also points out a very relevant side point:

> The consistency is sometimes a problem on  a piano with front rail
> punchings that are too soft.  After a good deal of playing with different
> things, I have wound up using the Renner-supplied  Bosendorfer punchings.
> What makes them superior is that they will maintain a consistent keydip
> with a variety of "touch"  (read "hardness of blow") - the result is that
> you have a sound (sorry) foundation on which to build the rest of the
> regulation.
>
>It's very advantageous to have a solid, secure end to key travel.