Hammer shafts and tone quality!?

[xvimbi]

I have a very technical question, but it has direct implications for everyone who wants to achieve the highest level of piano playing...

A good pianist is able to modulate the tone quality of a note by how the key is depressed. That is, given the same loudness, one can achieve different qualities, such as "harsh", "soft", "round", etc.

I was wondering how this possibility is built into the piano and what technicians or piano manufacturers do to adjust the action to allow a reasonable range of tone control.

Some background: The loudness of a note depends solely on the velocity of the hammer when it strikes the strings. The tone (quality) depends on how the hammer actually interacts with the strings at the moment of contact. The argument is that the hammer shafts have some flexibility that contributes to the "flight" properties of the hammer. The flex in the shaft does not only affect the effective velocity at the moment the hammer strikes the strings, but also adds additional vibrations that will create a different range of overtones, or in other words, will create a different tone quality. The amount of flex in the hammer shaft depends on how the hammer is accelerated to reach its final velocity at the moment it leaves the jack. Depressing a key with a constant velocity a all the way down to the escapement level will generate one kind of tone quality, whereas continuously increasing the velocity from, say, a/3 to a, will result in a different amount of flex in the hammer shaft and therefore a different tone quality.

Can anybody explain to me how a technician can adjust the flex in the hammer shafts? Shape and weight of the hammer are two aspects, but what about the material of the shaft?

[faulty_damper]

Actually, you are forgetting the most important part that has more to do with tone quality and that is the actual stricking object, the felt on the hammer.  That has more to do with sound quality than anything else.  You sort of glossed over it but new pianos usually have a nicer overall tone than used ones because the felt/wool compresses after lots of use.

Part of piano maintenance is voicing which the techy does to even out the tone or to voice it to the proper voice level.  I need a proper voicing but would rather do it myself.

My piano was "harsh" because the hammers were compressed at the point of impact.  But I softened it a bit using some very ghetto, but effective, methods.  It now has a nicer, more gentle tone to it and it sounds nicer.

[xvimbi]

Actually, you are forgetting the most important part that has more to do with tone quality and that is the actual stricking object, the felt on the hammer.  That has more to do with sound quality than anything else.  You sort of glossed over it but new pianos usually have a nicer overall tone than used ones because the felt/wool compresses after lots of use.

Part of piano maintenance is voicing which the techy does to even out the tone or to voice it to the proper voice level.  I need a proper voicing but would rather do it myself.

My piano was "harsh" because the hammers were compressed at the point of impact.  But I softened it a bit using some very ghetto, but effective, methods.  It now has a nicer, more gentle tone to it and it sounds nicer.

This misses the point. No question the felt is important to the overall tone quality of a piano, but this is not something a pianist can affect during playing. I am referring to the modulation of tone quality depending on how one depresses the key.

[faulty_damper]

I don't know.  I don't think a "harsh" piano can every be "sweet" no matter how you play it.  I've never played on a piano that had multiple tone qualities.  All of them had just one quality no matter how I pressed the keys whether it be fast or slow.

[xvimbi]

I don't know.  I don't think a "harsh" piano can every be "sweet" no matter how you play it.  I've never played on a piano that had multiple tone qualities.  All of them had just one quality no matter how I pressed the keys whether it be fast or slow.

The differences are subtle but clearly audible. However, only in good, high-quality pianos will this type of tone modulation be perceptible. Mastering it is absolutely necessary to play at the highest level. It is the reason why leaning into the keys, i.e. using a  lot of arm weight, will generate a different tone quality compared to leaning backwards with the torso and using mostly the fingers. The latter will sound harsh compared to the former, although the loudness might be the same.