aftertouch

[Roger Jolly]

Greetings Del,
                A great post, in my travels I find that jack positioning (
front to rear) and jack hieght is a frequently omited, and misunderstood
part of the regulation.
  For special performers I will push the the let off and drop to almost
1/32" with 10 to 15 thou of after touch. These specs feel great to the
performers but will not stand wide or prolonged humidity swings. The action
must also be in first class mechanical condition.
  Jack escapement and repetition spring tension is felt by the pianist, but
very few of them can describe what they are feeling. Consistentcy is all
important in this area, positive action is important, but sudden clicks and
jumps will definitely bring complaints.
  In my experience the Japanese factory techs are maticulous in these
areas, to fine tune any action it must be remembered that the action must
be regulated twice, due to the inter-active nature of hammer height, rep
spring tension, rep lever height,and jack position. Once all is well with
the action stack. then is the time to set the after touch, it needs to be
clean and solid to the touch. My final check is to check the consistency of
dip, this will quickly show any errors. Wide after touch can mask a
multitude of sins.
Roger  

>
>Stephen, et al,
>
>Basically aftertouch is required in the "modern" action to allow the jack
to escape. It
>must rotate enough so that the tip of the jack avoids the hammershank
knuckle as the
>hammer rebounds away from the string set after impact. If it does not
rotate enough it is
>quite possible that the knuckle will bounce against the tip of the jack
and cause the
>hammer and shank assembly to oscillate -- repeatedly and rapidly impacting
the strings.
>This phenomenon generally called "bobbling." Aftertouch can be viewed as
insurance. It is
>insurance against hammer blocking and bobbling. However! How much
insurance is actually
>required is really the question.
>
>Back when I was doing a lot of concert tuning and prep work I spent some
time working with
>several different performing pianists trying to figure out just what it
was that they
>wanted out of a performance piano action. Sadly, the first thing nearly
all of them said
>was that they wanted them to work! Always during these conversations I was
told the horror
>stories of the many so-called "concert" pianos simply didn't work very
well. Beyond that,
>they wanted the action to feel uniform and consistent, both in tactical
response and in
>voicing. Solid tuning was a given. They mostly expected -- and got --
that. Most of those
>horror stories were about action performance, often on very well tuned and
voiced
>instruments.
>
>Getting into the details of regulation preferences, most of them wanted
jack letoff to be
>as close the the string as possible without making the hammer block on
very soft blows.
>They wanted "dynamic" touch weight to be absolutely consistent. I found
that many, if not
>most, of those I queried could definitely feel -- and they did not like --
the
>inconsistent key leading most modern actions are plagued with. I.e., there
couldn't be
>four leads in one key and five in the next and then three or four in the
next, etc. This
>meant there must be an engineered and uniformly tapered leading scheme. No
"individually
>weighed off" keys for these folks! Irregularities in static touch weight
had to be tracked
>down and fixed. Rarely was aftertouch mentioned as such. They wanted key
travel -- i.e.,
>key dip -- to be as short as practical and as uniform as possible. And
they really meant
>uniform! More often, if it was used at all, the word "aftertouch" was used
in a way that
>really meant key travel.
>
>After playing around with different regulation parameters a bit I came to
the conclusion
>that what was really desired was as shallow a key dip as was practical.
This meant that
>with a hammer travel distance of 45 mm and a key travel distance of 9.5
mm, the actual
>key/hammer lever ratio should be no more than 1:5.4 and 1:5.1 would be
even better. There
>should just enough key travel and/or aftertouch to trip the jack and
rotate it far enough
>out of the way so that the tip of the jack would almost, but not quite,
fully clear the
>knuckle on a very soft blow when the key bottomed out. The returning
knuckle would
>complete the job of pushing the jack out of the way. For an action to work
reliably in
>this manner it requires that relative thin and firm front rail punchings
be used. Which
>was a good thing, since the pianists also wanted the key to bottom and
stop moving with
>some authority. Actions regulated this way demanded a fairly precise touch
on the part of
>the pianist -- generally this was not a problem. They appreciated the
challenge and the
>control. Ah! The control! The action might seem a bit overly sensitive at
first, but the
>pianist soon adapted and would soon start trying things they hadn't
attempted before.
>Actions set up this way also required slightly -- only slightly -- more
touch-up
>regulation to keep them working reliably. But my, were they ever quick.
>
>All of this does make me kind of wonder why current action configuration
and set-up is
>going the way it is. It seems to me that using heavier hammers along with
the requirements
>of additional key leading and/or lower (numerically) key/hammer travel
ratios is leading
>us away from this quick and responsive type of action feel. Key travel is
increasing --
>10.5 to 11.0 mm is no longer unusual. How far can the human finger move
with the speed
>required for some of the faster virtuoso performances? It seems to me we
should be trying
>to set up actions to make these performances easier, not harder. When I
started in this
>business, a key travel of 9.5 mm was considered the norm. Probably 8.5 or
9.0 mm would be
>even better. (Stephen, what is the key travel on some of these early
actions?)
>
>Well, I fear I'm beginning to ramble and it's been a really long day. If
anyone else has
>any thoughts and/or experience with this type of action set-up and
regulating I'd be
>pleased to hear about it.
>
>Regards to all,
>
>Del
>
>
Roger Jolly
Balwin Yamaha Piano Centres.
Saskatoon/Regina.
Canada.