Bluthner Patent Action

[John Alsina]

The following sentence from new translation of the Bluthner regulation procedure may explain much of the difference in touch 
between the Bluthner and the Erard actions:

The key should be pressed slowly until it comes to contact with the touch washer, 
and then the hammer should rise a further 1 millimetre before setting off, ..

This makes a big difference between what the pianist feels just before and during let-off on the two types of action.
On the Bluthner, the key contacts the front punching, and the finger begins to encounter smoothly increasing resistance before let-off.  At let-off, there is an additional "bump" of resistance due to friction between jack and abstract, but it is only a part of the total resistance felt at that point.  Depending on the quality of the punching and the exact let-off regulation, the "bump" felt due to let-off may be almost imperceptible.

On the Erard, the key doesn't contact the front punching until after let-off.  This produces the characteristic "notch" sensation of low resistance followed by higher resistance due to let-off friction, followed by lower resistance again, and finally contact with the front punching.

My personal impression of the Bluthner is that the progressive resistance and lack of notchiness at let-off produces a pleasantly elastic feel at the key bottom that gives excellent control (and therefore confidence) during soft, rapid playing.  Playing above pp, it feels the same as an Erard.  As an experiment, I have tried setting up an Erard action so that the key contacts the front punching before let-off.  I regulated let-off by placing a weight on the key and advancing the let-off button until let-off occurred.  This adjustment was very precise and repeatable.  This procedure 
produced a similar effect to the Bluthner action when playing softly - elastic feel, predictable let-off, excellent control - but it felt very strange and rubbery at higher volumes.

Any thoughts on why that might be?  Might there be a way to regulate the Erard to get the Bluthner feel at low volume without the rubberiness at 
higher volume?
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