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Seems a lot of people are interested in aftertouch.

The digital folks know it as a way to alter timbre, volume or whatever parameter once the key has bottomed out. Pushing on it after the initial strike allows for swells etc...

On a upright, aftertouch is tricky no? You play the note full circle in order to determine it? Dip etc.. Tell me if I am wrong please.

On a grand, I set let-off, drop and aftertouch at the same time. No aftertouch means not enough dip. Aftertouch is a test to make sure blow distance and dip are compatible, all other regulation being precise.

I would really like some tech to concisely explain aftertouch for the masses.

I understand it, but can't seem to explain it in a simple way.

Key aftertouch is insurance against "bobbling" hammers.

As the heel of the jack trips against the letoff button, the top of the jack begins to move—escape—out from underneath the knuckle. If the top of the jack does not move far enough it can block against the knuckle (butt, in an upright) as the hammer rebounds away from the string(s) and cause the hammer to bounce back against the string: i.e., the “bobbling hammer” problem. After jack letoff the front end of the key must continue to move down far enough after letoff so that the top of the jack fully clears the knuckle (or butt).

If key aftertouch is too deep the top of the jack can bind against the front of the window in the repetition lever. This both feels bad to the pianist—it causes a rather “spongy” feel to the bottom of the keystroke—and it puts a high stress on the jack and can cause them to break.

The proper amount of aftertouch for any action will cause the jack to fully escape—far enough so it fully clears the knuckle with the key fully depressed—yet not bind against the felt stop punching in front of the window of the repetition lever.

ddf

For musicians, aftertouch is literally, the after touch - the incredibly important feel of the end of the keystroke, determined by the length and 'shape' of the escapement and the remaining distance to the bottom of the keystroke. It is a metric for playing controlled passages and critical that friction is even. For playing pianissimo it is critical that the aftertouch be sure and precise, but not a sense of 'breaking through', as that actually affords less control.

So for musicians, aftertouch is everything - the beginning point of the escapement in the keystroke, the shape and feel of the escapement, and the remaining dip until bottoming out (including how the density of the front rail punching affects the give of the endstroke).

With technicians, many times I've heard aftertouch simply put as the remaining keydip after letoff; or also, the point of escapement.

To me, it's not defined by one thing. Aftertouch is the after touch: all the elements that take part in shaping the delicate end of the keystroke. It is what makes a good regulation. Aftertouch is, after all, what really makes the entire touch of the action that's most relevant to a pianist. It's a marker for distance traveled, an interface that's played upon for pulling the most delicate expression out of the piano.

Aftertouch is the quality of keystroke experience at and after the point of escapement, the length of keystroke after, and the quality of the endstroke. It is governed by virtually every part of the regulation.

I want to add: from an action design standpoint, I would say the same thing as Del - aftertouch is the precise amount of additional keydip needed after escapement to clear the jack, allowing fast repetition without interference.

And how would that last paragraph read for an upright, Del?



... umm, against what? On those actions that I've seen with a jack slap rail, this was adjusted quite far away from the jacks. Other actions don't even have a jack slap rail, but simply a thick strip of felt on the back of the let-off rail, which is even further removed from the jack tops. Given enough aftertouch / key dip, the jack could easily move 1/4" away from the butt leather and still not bind against anything. But that's obviously not right, and puts undue strain on the jack springs.

I've read that there should be a gap of about 1/16" to 1/8" between the butt leather and the jack when the key is fully depressed. Would you agree?

I'm sure Del can give a more precise answer, one effect of too much aftertouch (or too much key dip) in an upright is that the hammers will be checking too high - to the point where hammers may be blocking against the strings if the amount of downward motion allowed is extreme.

Compare aftertouch to follow-through in golf. You absolutely want follow-through, but also you don't want too much. Have you ever seen a beginning golfer swing so hard that they do a 360 - swing all the way around? Too much. Same with after touch. You don't want to hit bottom with the key at the exact moment of escapement. A little bit of downward travel is needed to complete the stroke - but not too much.

(Sorry for jumping in, Del. I'm sure there is more to be explained here that I'm missing.) Chuck

This interests me as well. Disclaimer...this post is mainly thinking out loud...no grand pronouncements.

From a pianistic perspective, I find, time and time again,the precise amount to of grand aftertouch absolutely crucial to a pianists experience of the action. Consistency of course is important, but the precise amount of aftertouch will make or break the touch of an otherwise perfectly set up action.

I have thought about and have read explanations as to why, as Chuck notes, "follow-through" is necessary. Something about the "after" part of escapement is important. Maybe it is simply "follow through". And I guess I buy it, but not completely.

Again and again I find, in fine tuning a fine grand action for a fine player, that a lowly green punching (.005") will often make a huge difference. I find it hard to buy the "follow through" explanation here, just because of the tiny change in absolute terms .005 makes. In relative terms, .005 is 12.5% of an .040 aftertouch... maybe more believable here, but something still bugs me in the oversimplification department, and I can't put my finger on it (...uhh, in a matter of speaking...).

It would be interesting to break down exactly what the chain of physical events that encompass the full follow through motion are.

...pondering...

Jim Ialeggio

Personally, I believe that the "mystery" of aftertouch lies in the player's perception of two components:

1) The presence, or absence, of an abrupt end to each keystroke, as opposed to a smooth transition from downstroke to upstroke

2) How quickly, and responsively, the edge of the key rebounds back into the player's finger after bottoming out on the front rail punching, and how far the finger has to travel before that happens

Some excellent points which most of us can agree on.

One problem is that aftertouch changes by much more than .005", depending on the way the player depresses the key. This depends of course on the squishability factor (technical term) of the front punching. Depending on the softness and thickness of the punchings the variability in aftertouch can be enormous. (Speaking here of the measured key stroke, of course) I would say you can get a measured difference in aftertouch of about 1 mm (.040") with different attacks, if not more, from pp to ff.

A firmer punching that does not compress so easily while at the same time having enough resilience (=springyness - another technical term) to absorb and dissipate the key's energy while avoiding the key thump is of great advantage here.

Crescendo front rail punchings are probably the best choice available to provide a consistent and precise aftertouch. The resulting touch sensation instills confidence into the playing of the pianist, because he/she knows exactly where the key will bottom out with every keystroke, no matter the dynamic called for. Often, replacing the old cloth front rail punchings by Crescendos improves the tone of the projection of the piano. I know some may find this difficult to beleive, but this is the finding of many different and independent technicians and players.

I'm really glad someone has put a name to this! For a long time, I understood it but couldn't put a name to it. That is a perfect word, "aftertouch"! Perfect.

It's the secure feeling of the key under you finger, with that "bounce" action that let's you know that key is there because you can "feel" it. It's what makes playing a particular piano so much FUN! It gives you a little lift or fight, not too much fight, but rebounds with that pleasurable feeling that has been hard to describe up until now!

This is that feeling that makes one go back to that particular instrument time and time again. And in search of it when you try out a different piano. One is hoping that bounce "aftertouch" is there.

Thanks to all you for explaining the physical action on the piano that makes this happen and your explanations were amazing! Much appreciated!!!

See how quickly a request for something "simple" explaination can get complicated? The original post from Accordeur read, in part:

I realize a good chapter of a book could be written on the subject of aftertouch—that is the complicated explanation—but the request here was really for a simple and concise explanation.
I realize my little explanation leaves out a few things. As I look back over what I wrote late last night I wonder what else I could have left out in the name of simplicity and still had it work.

ddf

Greetings,
How about, "Aftertouch is the last, small amount of the key's travel after it has finished lifting the hammer".

I find it effective in selling regulations. I have a customer learn to recognize aftertouch on the ends of the keyboard. Once they sense it, finding notes in the middle of the piano with none helps sell the job. A big part of what we do is education. Those that are good at it can often build a trustworthy clientele, since the more the customer knows, the less interested they become in poor work.
Regards,

Note that when a player responded to this thread she used the following words (in bold):




That is why I described it the way that I did earlier. It is NOT just the extra travel of the key on the way down that they are perceiving. They also want the key to feel a certain way when it finally bottoms out AND bounce back up into their finger as they prepare for the next repetition, or move to the next key. That is all part of the sensation of "aftertouch".

Think of it as analogous to a car. When a car is new and everything is adjusted and working properly, the bumps in the road are smoothed out nicely by a finely tuned suspension system. The springs, shocks and tires all work perfectly to allow the car to dip and return just enough to give a perfectly smooth ride, which is perceived as "comfortable" by the passenger. If the shocks or springs are too stiff, then there is no give and the ride feels hard and unforgiving. If the springs and shocks are shot, then the ride becomes overly bouncy, as the body of the car moves too far in each vertical direction before returning to level.

Thank you Mr. Fandrich. I started this thread so that the folks over in the piano forum could understand the basics of aftertouch. Your post explains it much better than I could. Thanks again.

Jean

I just adjusted aftertouch on a used grand today in the store. I had to remove approx 0.030" of punchings to get aftertouch. The two piano teachers played it before and after and could not believe what a difference it made in the "feel" of the piano. Also adjusted let-off and drop.

I like that!!! Very well said! Conciseness at it's best!!! Mr. Foote, you win the prize!!

That last little "feel". That little "squish factor". The kick back, the antagonist, the friction, the feeling of a complex mechanical system at the the tip of your fingers.

Stages of friction and weight. Dampers, let-off etc...

As a piano player before becoming a tech, I already was capable of making a shitty instrument sound good.

Now that I know better. Mr. Fandrich said it well. Aftertouch is insurance.

Most often, on an older piano the reason for no aftertouch is not because the dip is too shallow. It is because all of the action felts such as wippen heel felts etc have worn and compressed somewhat. As a result, the blow distance has grown to 50 mm or more. Measuring blow and dip is where I would start. Often, the front rail punchings have also compacted, which needs to be compensated by adding paper punchings.

I am not saying this was the case in Les' piano and that he did the wrong thing, just outlining a typical scenario. There are always different situations, one extreme being growing action brackets which first gobble up after touch then move on to blocking hammers and a total regulation mess...

It would have been more helpful if I’d said, “Aftertouch is insurance against “bobbling” hammers.”

ddf

This was on a 8 yr old Yamaha grand. Started with bedding the keyframe and adjusting the balance rail. Raised the hammer line to spec, blow distance was maybe 1-2 mm's low. The dip was to shallow, less then .394 but key height was right on. In order to get through let-off on some keys, you had to apply additional pressure to the key. After setting my sample set, it felt good so I did another sample set in the treble.

After touch is extremely important. So is being consistent with having it. With no after touch, the feeling in the key is very different than it is with proper after touch and will often be the cause of double bouncing (bobbling) hammers.

1-2 mm's can be quite a lot of difference actually when it comes to pianos. What we do in the front of the key, say, with key dip for example, makes a lot more difference by the time we go to the backs of the keys and into the action.

After touch does not always mean, increasing or decreasing key dip or key height to attain the right, final "feel" of having after touch. Addressing it from that perspective only, might just throw you off as it is not always the right answer or the right solution to the final outcome. Keep an open mind at all times. Sometimes there is another answer such as raising or lowering the hammer line a "tad" instead. It does not take much, to make a difference.

Proper key height and dip, is always essential in every regulation job and it almost always consists of some give and take here and there. In other words, what many techs forget, especially the newer techs is that factory specs are merely a guideline to get us within the ball park of "approximately" where things should be. From that point forward, we do the remainder as my dad always said, "by the seat of our pants." Whatever makes it work the best, is what we do. If that means, adding a little bit more key dip, okay. Or, maybe it means, increasing the hammer line or decreasing it instead? Trial and error is sometimes required to attain the best and most accurate results.

My 2 cents:
Aftertouch is how much the key travels after let-off is complete - all things being equal.
All things being equal meaning that the action is completely regulated - aftertouch is usually the last adjustment that I make.
Too much aftertouch and you risk pushing the jack against the stop felt, too little and you risk bobbling hammers. (this window is the limits)
As Jurgen mentioned about Crecendo punchings, I really like them and they give a very definite feel of a completed key stroke.
In either case, if I set aftertouch using a weight and spacer I get consistent results regardless of the type of front felt punching.
Is there such thing as aftertouch in an upright action?

Yes, there is aftertouch on an upright action.

Blüthner actions specified that there be no aftertouch.

BDB, Where did you get the spec of 'no after touch' for Bluthner's???

From the spec sheet that Blüthner provides. That is for the old Blüthner action, not the Erard style actions they use today.

Here is a link on their UK website to advice on how to produce a good touch with the [historical] Blüthner action in a Blüthner Grand.

It says the jack should be released from under the nose of the abstract when the key is lightly pressed on the touch baize. No after touch is necessary.

André van Oorebeek advised me on applying a similar principle to an upright. The backcheck needs to be adjusted such that the hammer moves forward by 0.5 mm when the key is lightly pressed. My interpretation of his advice is that the point at which the jack escapes, and the upward part of the action cycle is complete, should coincide with the key reaching the cushion.

On has to decide precisely when the jack has reached that point, and that may depend on how much insurance you want to provide. If you are taking risks and the checking is close I think a firm punching could be better as Jurgen said.

Only if the backchecks aren't adjusted properly to the larger aftertouch/dip. I was assuming that the backchecks were properly catching the hammers in both cases, and wondering whether there's any other difference between small and large aftertouch/dip.

Yes, there is. The face of the jack will interact differently with the butt of the hammer making the feel of letoff different.

This, aside from the possibility of the jack hitting the rail as a physical constraint.

Smaller aftertouch generally creates a softer, more spongy letoff feeling. Larger aftertouch generally creates a sharper, harder feeling.

Posted:
>>Smaller aftertouch generally creates a softer, more spongy letoff feeling. Larger aftertouch generally creates a sharper, harder feeling. [/quote]

Greetings,
My experience is exactly opposite of that. Minimal aftertouch makes for a hard landing, softening as aftertouch is increased until a point is reached where the pianists complain of not knowing where the bottom is, feels mushy, or sometimes referred to as "swimming" in the keys.
Regards,

Dear Ed,

Agreed! Minimal aftertouch is the 'hard landing', the abrupt clank of hitting the bottom suddenly and sharply. Too much aftertouch is the spongy 'where am I?' vagueness that feels so mushy and undefined.

I always think of LaRoy Edward's explanation, from the Yamaha view, of aftertouch.

Think of the keystroke as walking down a flight of stairs. If the bottom step is shorter than you expect, you nearly trip, and your foot finds the bottom abrupt. If the step is deeper than you expect, you nearly fall, as the foot searches for that landing spot. When the step is just right, you step cleanly off the staircase, and move freely and comfortably.

That analogy works very well for understanding the 'feel' of aftertouch. Getting it to work in an action is the puzzle! Given an adequate and equal keydip, close to the correct parameters, I will raise or lower the hammerline to find the right aftertouch in a given piano. This gives the quickest and most effective way of quickly changing the aftertouch, and feeling, of a mostly well-regulated piano. Mind you, the piano must have correct let-off, drop, and spring tension...all the basics must be correct...but once that is accomplished; small changes in the hammerline, up or down, can give the final polish to the fine regulation of the piano.

Sipping the morning coffee,
I am,
Endlessly fascinated by these things,

I think two things are being confused here.

The abrupt ending of too little aftertouch can be interpreted as a sharp ending and too much aftertouch can be a spongy nebulous feeling - in terms of key distance.

But a musician's sense of it is more nuanced and complex.

Aftertouch is not just the key distance to the bottom of the front rail after letoff.

Here, I was trying to bring attention to the feeling of the jack moving against the knuckle or butt of the hammer.

Jeff writes:
>> Given an adequate and equal keydip, close to the correct parameters, I will raise or lower the hammerline to find the right aftertouch in a given piano. This gives the quickest and most effective way of quickly changing the aftertouch, and feeling, of a mostly well-regulated piano. Mind you, the piano must have correct let-off, drop, and spring tension...all the basics must be correct...but once that is accomplished; small changes in the hammerline, up or down, can give the final polish to the fine regulation of the piano. <<

Greetings,
I agree that it is polishing the action. I am sometimes drawn to an even more obsessive polish, which takes a lot of time, and is invisible to most pianists, but can sometimes impress the most onerous ones.
In a concert setting, I will set all the key dip exactly the same. Then, after the let-off and blow are set in the piano, I reset the keydip so that all aftertouch is identical. I first change the dip, but if I can't get the aftertouch correct with a .008" alteration, I then move the hammer to bring the aftertouch into line. I think by splitting the difference between blow and dip to keep a consistent aftertouch, the minor inconsistencies of any action disappear.
It helps when setting up a keyboard to place a blue and pink punching at the very bottom of the front pin before setting all the keydip, so that when the final regulation is taking place, you can easily subtract a known amount from any key. This also allows a rapid global change of keydip if an artist were to request it, by taking out a pink, or a blue, or both from every key, leaving the relative equality of aftertouch settings stacked above them unchanged.

It is a lot of work, and only worth it in a few selected venues, (and places like Ronnie Milsap's piano, which is subjected to closer tactile scrutiny than any other piano I believe I have worked on!).
Regards,

I started this thread to keep it simple, but I must say this post is awesome, excellent ideas, especially about having an even amount of punchings at the very bottom, allowing for easy modification at a later date. Thanks very much.

I'll second that Jean....

OK. Since this has gone and gotten complicated…

The problem with determining a “proper” amount of keydip and/or aftertouch can be traced to the large radius—I know it is not (usually) a true radius but it will do for the purposes of this discussion—of the area of the hammerbutt covered by the leather. The knuckle on a grand hammershank typically has a diameter of 9 – 11 mm (a radius of 4.5 – 5.5 mm). A typical upright hammerbutt “knuckle” diameter might be 15 – 16 mm (a radius of 7.5 – 8.0 mm). Even though the lever ratio between the heel and the tip of the grand action jack is much lower than that of the upright action jack the tip of the upright jack has to travel quite a bit further to clear the returning hammerbutt.

There is a relationship between the amount of aftertouch and the hammer back check distance from the strings although it is not necessarily an obvious one. With the key fully depressed with “normal” finger pressure and the hammerbutt assembly in check the tip of the jack should just clear the hammerbutt lever. Much less aftertouch than this and the action starts to exhibit a propensity to “bobble.”

Addendum: I once modified a set of upright hammerbutts to accommodate large—11.0 mm if memory serves—grand hammershank knuckles. The hammerbutt felt was normal and the intersection point between the tip of the jack and the knuckle was the same as with the original butt leather/felt sandwich. The difference in regulation precision was dramatic. It required less aftertouch for a clean, positive letoff feel. For the duration of the time I had the piano in my shop the folks who played the piano loved the action feel; it was much more precise than the original. Still, I’ve been unable to get any action maker to even try making an action with this configuration.

ddf

One could probably then improve the feel of a vertical action by careful bolstering of the butts, similar to what is done to grand knuckles. It would also seem that bolstering grand knuckles would increase the radius of a flattened knuckle.

Guys, what about adding the "Touchrail" to the mix? http://pitchlock.com/touch-rail/ Not being a piano tech, I can't comment on it from a tech standpoint. What in your view are the pros or cons if any, of adding this device to a piano, assuming that the all regulation has been done before adding the Touchrail?

That's interesting, Del.

That mirrors what I've felt in actions but I'm glad to hear someone else felt the same.

So a smaller radius body of rotation against the flat face of the jack results in a more clear and pronounced letoff feel - as the edge of the jack interacts with equivalent weight concentrated on a smaller cross section of surface area.

Thanks for sharing this experience (with measurements).



This is exactly what I was talking about above. In this case, a smaller radius knuckle interacting with the face of the jack was able to achieve a more precise letoff with less aftertouch.

Touchrail:

To answer Grandpianoman's question on the touchrail, I thought I would just add it here.

The touchrail is only what I call a 'triage' measure. It is a quick, low budget measure to achieve a reduction in downweight.

It works due to the vertical and horizontal components present when energy is transferred to the bottom of the knuckle from the jack. By starting the key partly along it's initial path of travel, this horizontal component is prevented as much from engaging (where most of the resistance occurs).

Assuming a good regulation, this might be a fun way for a pianist to experiment with downweight changes. Another reason to install would be if the client wanted a touchweight reduction in the cheapest way and wanted it to be 'resettable'.

I would never install this for any other reason.

I don't see any big cons to this device, it just doesn't take the place of regulation or real touchweight work. There are small springs over each key, backed by felt that prevent the key from returning to its full rest position. They are difficult to precisely control. This also raises the hammer line.

It's a quick way to achieve a different feel.

This also brings up another interesting topic related to touch: the touchrail works on the principle that downweight is not a constant but governed by a sinusoidal curve.

This thread is about after touch. Touch rail has no impact on after touch, as the effect of the springs is reduced as the key gets depressed. There is a net zero effect of the system by the time the hammer reaches let off.

I appreciate your intense concern for the purity of this thread, but I'm sure it will hurt no one to explore a little and have conversation.

Was the dramatic difference associated with reduced key dip?

Jim mentiond that 0.125 mm punching can make a huge difference, perhaps most noticeably to the feel of the key returning as Chopin Lover described.

On the figures the jack would have had to travel 2 - 2.5 mm less far to clear the knuckle than its usual hammerbutt so, presumably, key dip was significantly reduced and perceived responsiveness increased.

Is the implication that some uprights with anti-bobbling insurance may have a bit more aftertouch than many folks would actually prefer?

Aftertouch on an upright is measured by playing the note full circle. Mezzo forte. The back check regulation is crucial in determining it. The squish factor of all felts, especially the front punching, is crucial as well.

On a grand, measuring aftertouch does not involve the catcher. Very soft play, hammer does not even reach the string. Let-off, drop, aftertouch. The squish factor is still there, but not nearly as much as on an upright.

All of you who are better at writing than me. Please go on.

I wish I was as good as Mr. Fandrich, Mr. Foote and others at being concise and clear.

Hey Ian, I'll try to help clarify. There's two things at play here - that are partially codependent. Letoff feel and final key travel (or aftertouch).

There was a dramatic aftertouch difference in Mr. Fandrich's action despite reduced key dip.



This was because of the installation of a smaller radius grand knuckle in the hammer butt, lending to a sharper concentration of weight on the jack face and a more positive escapement feel.

Uprights typically need more key dip to achieve positive escapement feel because:

- the larger 'radius' butt requires this due to less precise weight loading

- that 'radius' needs more jack clearance to avoid bobbling



There are two separate implications; one having to do with knuckle or butt radius, and one having to do with amount of key travel, but yes, this is one conclusion I think Del was pointing to. Despite increased jack leverage in the upright, necessary aftertouch distance had to be greater in the key to prevent bobbling against a larger 'radius' butt.

I hope this clarifies?

Yes many thanks, Tunewerk.

I haven't put a hammershank knuckle in my upright but I'm inclined to think the key dip required for the jack to clear the butt is the major factor.

What I have tried is reducing key dip by 0.25 mm and 0.5 mm and catching the hammer closer to the strings to prevent bobbling. This makes a really big difference to the feel of the keys. Ed Foote's and Jim's post make me think 0.375 mm might be a happy medium between responsiveness and follow through.

I am slightly sceptical about the feel of the jack making such a big difference. The reason is that the momentum of the hammer assembly will lift the butt off the jack as soon as the let off button interrupts the jack's vertical movement. I do realise there may be a small amount of frictional movement between the tip of the jack and the butt leather during "lift off", and it would be great if anyone can explain precisely what happens at that instant.

On a grand, one point I would make is that it is helpful to have the letoff and drop set so that the jack tender hits the letoff button and the repetition lever hits the drop screw at the same time. This provides a definitive feel of escapement, and can only help in the attempt to set consistent aftertouch.

Otherwise, lots of good thoughts here. I like Ed's point that a big part of our job is education. So true.

I did this some years back so forgive me if my memory is off a bit, but….

In a full-size upright action with a hammer blow distance of ≈ 45 mm and backcheck distance of 15 mm the jack has to rotate through an arc of approximately 22.5° for the tip of the jack to fully clear the slope of the hammerbutt. With a hammerbutt radius and shape resembling that of the grand hammershank knuckle it needs to rotate through an arc of only about 15°.

With the typical hammerbutt contour the jack has to slide quite a great distance (relative to the grand jack) just to go through letoff and then it has to continue traveling quite a bit further to clear the contour of the hammerbutt. If you have access to a grand action model and a vertical action model you can study the motion of the respective jacks and see the difference. Visualize the shape of the grand hammershank knuckle superimposed on the upright hammerbutt.

If the pianist has a fairly controlled and precise fingering technique aftertouch on a vertical action can be reduced slightly without causing any particular problems. But if the keys are not always fully depressed during slow pianissimo passages it is best to provide the extra insurance of just a bit more aftertouch. However it is set, the “feel” of aftertouch with a vertical action is less precise than that of a grand action. But it doesn’t have to be this way.

ddf

The full circle is the problem on an upright, I think. Instead of allowing the jack to go straight back where it came from, the design of a conventional action forces it to describe an arc of 22.5°, there and back, according to Del's drawings. Del's knuckle experiment showed at least one third of that movement is musically unnecessary.


No doubt my knuckles will be rapped for venturing into design territory but here is a diagram of a Renner vertical action.



As I see it, when the jack rises the angle between the jack and the red felt will close and a similar angle, rotated by 90° anticlockwise, will tend to open up between the top of the jack and the butt. I say tend because the wippen will be pushing the jack into the leather. It took me a while to realise that this means there is nothing to impede the jack rotating sideways after it touches the let off button. This is because the butt will continue to rotate at its current speed and be out of the way as the upward drive of the jack slows down.

Once the butt has separated, the jack itself will be happy for the key to reach the front cushion at any time. This means that aftertouch, measured round Del's arc, can be anything from roughly 5° to 15° or more if you wish. Of course, the backcheck has to catch the hammer, and that's where you need a designer.

The tuner was aghast at first when he found my piano with less aftertouch than he was expecting and checking close to the strings. As he was leaving I said I was going to put the action back to where it was. He told me to leave it, those trills.

So I agree with you, Del.

Through much of what is considered “normal” playing conditions you can be forgiven for being at least a little bit skeptical. It is only when the piano is being played at pianissimo levels of key force that letoff becomes an issue for most pianists. When the keys are being depressed slowly the consistency of letoff and aftertouch becomes a significant factor for many, if not most, pianists.

ddf

I'm a newbie at this, and here are two observations I made about aftertouch. Perhaps someone could comment on them in case I am in error.

1) When a key has "aftertouch", I noted that it is felt as the jack extrudes out from the repetition lever slightly before it swivels forward against the letoff. On keys that do not exhibit aftertouch, I noticed that the jack tends to start swiveling forward before it starts to extrude from the repetition lever.

2) The jack extruding from the repetition lever can be controlled by the drop screw adjustment.

So it would seem to me that the hammer drop amount should also match the amount that the jack extrudes from the repetition lever. And this can also control the aftertouch. So if this is true, wouldn't it make sense to adjust the drop instead of the keydip/hammer blow distance? It almost seems too obvious, which means I am probably mistaken somewhere in my logic.

aftetouch intention can be measured and regulated by differnt ways, one of the factory method is to determine how much hammer travel will give the correct key dip then install the hammer rest rai at the correct location and thickness. Then you are sure to keep the key dip the piano was designed for.
Indeed you have to know first :

Key height that correctly position the capstan/whippen relation

Original keydip (on a vertical around 10 mm more prone to be less on a small piano)

Theoretical hammer travel distance with new hammers (not worn out) that one is the one that can be find if unknown.

There are more than one stage in those operations, first hammer travel/or/and key dip are regulated ^so the jack is around 1 mm from the butt leather at full dip (very moderate pressure)

location of the hammer at full dip, after having bend backwards the backcheck rod of the sample notes will allow to really have a precise "pressure" regulation, with too much hammer travel for instance, the hammer head will finish its course too much near the strings (this is the opposite of how it reacts when the final checking regulation is done, the, with thin paper punchings)

If not when you think you have the correct aftertouch, very often the key is not at full dip, only retained by the backcheck stop (and you feel a strong springy sensation due to the backcheck wire).

Once the normal aftertouch find on samples, capstan is turned so the jack can trip under the knuckle, but there is not really lost motion.
(Hammer the action and do that again)

checking distance is then regulated on the sample notes, all backchecks are lined and straightened control up and down (control of backheck angle if somebody changed it .

Then notes are played 4 by 4 chromatically, then the ones that finish too near the strings,are showing small uneveness in key dip, or uneveness in the part dimension.

A small paper is used to get the good checking distance or/and slightly bending a few rods (it may not be too much apparent)

The original method to find the correct pressure reserve is easy when the action is new (the jack in the end of its trip avoid the hammer to come back) Less precise on a worn action, but the method still is what I use, particularely when I have repetition problems as on some U1 / U3

The location and corrrect tightening of the rods that hold the letoff buttons may be verified prior to any intervention.

Action hammered, and things checked again once.

On pianos with wooden capstans, the touch can be tweaked one direction or another by changing the location of the contact point, but this may stay accepteable in regard of the magic line, as it will change the way the acceleration is felt.

In a correctly designed, positionned and regulated action the hammer will have the same "drop" move as in a grand piano, more or less, during aftertouch.

too short hammers or bad alignment in the vertical plane can make that move absent, as stiff pinning, old return springs...
(sustain pedal engaged is better to check that sort of things)

Del you had a good idea. I believe the softness of the vertical but is necessary however, more than in a grand where firm knuckles are used those days.

Not for soft playing but to guarantee a longer jack/butt contact at higher level of velocity, may be (?)

SO to say, it have been discovered that the jack/knuckle contact is lost almost immediately when playing above mf (if memory serves those where the Pfeiffer's findings)

Conclusion was that the finger loose contact with the hammer very soon in most modes of playing. Vertical action with its low inertia is then less agreable.
Level of acceleration where the contact is kept with the hammer is very small.

Having a larger contact surface is may be necessary to retain the jack contact longer.

Jeff, this is an excellent analogy!

Stairs sure can be taken for granted, until you run across one that is a different size. To take the analogy a step (haha) further, I suppose one might imagine that flight of stairs being made of various materials, in addition to being different sizes. One step concrete, the next rubber, then wood, then foam. Never know what you're going to get.