[pianotech] Understanding Aftertouch

[Ed Sutton]

Steven-

There is "basic" aftertouch, and then there are many subtleties. 

For "basic" aftertouch, when the hammer is in check and the key is at the bottom, on the cushion in a normal resting, but not "squished" position, the jack tip should be in between the knuckle and the front wippen window felt. It shouldn't be touching either one. 

Notice that you can make subtle changes by adding or subtracting punchings from the balance rail or the front rail, or by slight changes in the capstan. When you have done all the regulation points "to spec," you still need to check, and make these little adjustments to get even aftertouch. (We'll have a class on this in Grand Rapids this summer.)

Another way to get a sense of good aftertouch is to examine a well-regulated new grand piano. Hold your hand out flat, and use the palmar surfaces of your fingers to slowly press down four keys. Press down slowly to the moment of resistance, then press a little harder to feel the bump. The bump is the aftertouch. All four keys should feel the same. Test the piano by pressing all keys in groups of four. If there is any irregularity, you will feel it. 

If, when you press through the bump, all four hammers just barely sound their strings, you have an extrememly well-regulated piano.

Ed Sutton
  ----- Original Message ----- 
  From: David Skolnik 
  To: pianotech at ptg.org 
  Sent: Monday, April 20, 2009 9:06 AM
  Subject: Re: [pianotech] Understanding Aftertouch


  Steven Hopp and friends -
  I think your main question has gotten somewhat diluted by side issues.  For example, any particular preference of tactile characteristics of the various types of front punchings is, for the most part, irrelevant, as is the question of any differences in the orientation of a conical punching.  Nor do I think that observing hammer rise is a particularly precise measure or way of understanding the connection between the mechanical process and the player's perception, though there it provides a definite visual correlation. 

  Read the recent thread titled "Erwin's Key Dip Gauge"  (2/27/09) for a totally informative discussion.  While I might differ with some thoughts there, the basic ideas are extremely enlightening, unless you already knew it. I realized that most of what I was about to contribute to your question seemed better articulated by some posts in that thread. I came up with some experiments just to be able to see and measure the effects for myself, but the questions about how much aftertouch or how hard a termination is desired by a particular pianist is distinct from (though related to) the fundamental mechanics.

  The relevant issues are:
  - What is aftertouch?
  - How is it measured?
  - What can a sensitive player perceive? 
  - What does a player want?

  Aftertouch refers to the movement of key and action parts that occurs after the jack ceases applying upward force to the knuckle.  Apart from any other arbitrary parameter, the space between the proximate side of the knuckle and what Steinway calls the Repetition Felt Block (#38 on schematic) defines the range limit of aftertouch.   Further travel will cause jacks to jam or possibly separate at the glue joint.

  Apart from any issues of preference, the Wurzen punchings are extraordinarily revealing about aftertouch and key dip, removing a great deal of subjectivity to the expressed measurements. In fact, applying a meaningful unit measurement to aftertouch requires a defined start and stop point and, of course, a specific object to be measure: the key.  An important point to remember is that the only way to come close to achieving consistent dip with consistent aftertouch is to begin with an extremely accurate key level - especially when using Wurzen conicals.  That means employing .001" and .002" paper at the balance rail, when indicated. 

  To experiment: with appropriate regulating applied (key level, hammer blow, rep lever height, springs (roughed), jack to knuckle core, drop turned down enough to allow let off, knuckle treated with teflon powder)    
  - (with damper raised) place leads on key so that jack will not escape except for the addition of one additional gram, placed at front.  Repeat for consistency.  You might want to tape leads in place. 
  - build up at front pin, using Wurzens and at least one cut punching of a target aftertouch (others if there is space) in the range of .020" to .040".  Fill in with card until almost at let-off. Continue with thin paper until one white (.003") will prevent let-off. 
  - Withdraw one of cut punchings and assess aftertouch.  Too much? not enough? Reinsert and pull different punching.  

  It's not a production method, but useful as a way of sensitizing you to the differences in feel.  Of course, in reality, the density of the front punching does make a considerable difference in the 'effective' aftertouch.  In more forceful playing, aftertouch is much less of an issue than 'stop-speed' (hard or soft punching) or depth (follow-through) sensation, but in softer playing, the uniformity of aftertouch is more of the issue, along with, of course, the transitional frictional differential in the actual let-off process...another topic.

  David Skolnik
  Hastings on Hudson, NY




    I am trying to grasp the production and feeling of Aftertouch in a fine regulation.  Can anyone explain how much a person who plays the piano normally can feel or tell if there is aftertouch.  I have read all of the PACE materials on the subject and some other sources, and while they explain how much in thousands the key dip might continue and looking for wippen and hammer rise they don't say how much for the last two.  It seems that viewing hammer rise to gauge aftertouch would be the easiest to determine.  
     
    So how much does or should the hammer rise be?  
     
    When the cycle of let off and drop is complete how much pressure on the key is needed to see or feel the aftertouch that is or is not present?  (the pressure required to push a button on an elevator or enough to feel the FR punching compressing)
     
    I recently posted that I installed the crescendo conical punchings on my Yamaha G3.  I am not sure how I feel about them.  I am trying to decide whether they are just too hard (and noisy) or is it that I do not have enough aftertouch to allow for the keystroke to slow down enough at the end of the motion to produce a softer bottom to the stroke during normal playing.  
     
    I hope this makes sense and appreciate any help.  I am planning to take regulation courses on Wed. in GR this summer so if I don't have it soon I am sure I will get it by then.
     
    Steven Hopp
    Midland, TX

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