What matters most ?

[A440A@aol.com]

Bill writes: 
<< I mean, a key of average inertia 
with a top action of excessive inertia sitting on top of it probably 
behaves no differently than a high inertia key with a normal top 
action sitting on it. In the former, the key is ready to accelerate 
as easily as we'd want, but its motion is is restrained by the 
sluggish top action load. In the latter, the top action is ready to 
accelerate as fast as we'd want, but its motion is provided solely by 
the key underneath it which will always be too slow. >>

    I think there can be differences.  Let's not forget that an action can 
reach a point of "saturation", in which the flexibility of the action comes into 
play.  When this happens, further force applied to the key will NOT transmit 
into more power reaching the string.    Keys bend when played, and the higher 
the inertia in the top action, the more that stick flexes.  That is one reason 
to minimize the inertia in the top action. 
    A longer knuckle placement with a shorter key ratio translates into less 
key weighting,(all other things being equal) and less flex in the key. This 
will require deeper keydip, but that also helps raise the saturation limit.  We 
would then have a higher saturation limit unless there is increased shank flex 
to cancelled the effect.  This is one reason that I think there is a 
different feel to actions of equal "weight", depending on whether they got their 
overall ratio by short key ratio with long knuckle distance, or vice versa.  
Still plenty to think about, though. 
Regards, 
Ed