aftertouch / hammer striking distance

[A440A at aol.com]

<< At the Yamaha Academy they teach that a perfect after touch is when  

one depresses the key, one goes through the motion of let off and  

drop, the key then rests on the front punching, and if one presses  

lightly, there should be a slight hammer movement of 0,4 mm.

The 0,4 mm is a healthy average movement.

It ensures an 'extra' after let off and drop have taken place, so  

that the jack can easily escape from under the knuckle, and  

especially during ppp, always a danger zone.

The 0,4 mm is a very tiny distance, but it is enough and it also  

creates a certain 'touch', a certain feeling.

It is safe and comfortable. However, because the movement is 'extra',  

it is also a little bit of a waste. A waste in movement, a waste in  

time, and thus a waste in energy, but, nevertheless, it is  

comfortable and, when executed correctly, always gives the technician  

a maximum of power. >>

Greetings, 
    Ok, there are some things I am confused about here.  In the event that it 
is a semantic confusion, I will list things in order, so that I can be 
brought to my senses about this. 

>>"the key then rests on the front punching, and if one presses  

lightly, there should be a slight hammer movement of 0,4 mm."

      I can make the hammer move .4 mm with a wide variety of aftertouch 
dimensions, so I can't understand how the above description applies to the amount 
of aftertouch.  "pressing lightly" is a highly variable quantity. 

<<"It ensures an 'extra' after let off and drop have taken place, so  

that the jack can easily escape from under the knuckle, and  

especially during ppp, always a danger zone."

        The jack escaping is where I cosider aftertouch to begin.  The key 
contacting the punching (with some degree of force, to be considered later), is 
where aftertouch ends.   I don't understand where the "extra" quality is, 
since I consider the travel of the key after escapement to be the "extra" an 
action needs in order to be dependable. 

>>" A waste in movement, a waste in  

time, and thus a waste in energy, but, nevertheless, it is  

comfortable and, when executed correctly, always gives the technician  

a maximum of power. " 

      I don't understand how the various amounts of aftertouch change the 
power, unless it is changing the blow distance.  All aftertouch is, at some 
level, a waste.  There is no more impelling power to the hammer after escapement, 
so it doesn't help with acoustic power.  Since the key return distance required 
to reset is increased, the more aftertouch for a given set of let-off, 
blow,and drop, the slower the repetition will be.

      I set aftertouch by using a shim (varies from .020" to .035") on top of 
the punching, after blow and let-off are set.  I have a highly developed 
sense of pressure in my fingers, (as, I think, all of us that regulate pianos do), 
and after getting a consistant blow, let-off, and drop set on consistant 
springs, that sense of touch is the final arbiter of what the keyboard feels like. 
 I have learned to trust my sense of touch, and even though the actual 
key-dip may vary by a small amount,(less than .006"), and the blow may be adjusted 
slightly to accomodate geometry that would require a keydip greater or lesser 
than this amount, the goal is to have the aftertouch consistant. Pianists have 
unanimously agreed with me that a keyboard felt more consistant when I went 
from a keydip to an aftertouch priority. 
     It is more evident to pianists that the aftertouch varies by .006" than 
when the keydip does by a like amount, since that .006" is 23% of the 
aftertouch, but 1.6% of the keydip(assuming a .375 dip).  Under very slow key 
movement, as in ppp, the finger forgets how far it has moved before it plays the note. 
 Also consider that many notes are played by depressing a key from a position 
already partially depressed, so the total amount of keydip is moot.  
 

Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html