Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum How Does Escapement Make it Easier To Play Softer?

I’m a hobbyist technician studying the craft, so I’ll start with a quote from Igrec’s Pianos Inside Out:

“Let off has two opposing requirements: to allow the jack to support the hammer as long as possible during its rise, in order to give the pianist maximum control in soft dynamics [emphasis added] - but let the jack escape early enough to prevent the hammer from bouncing between the jack and the strings, or jamming the strings. Every millimeter of additional distance from the strings significantly compromises control in ppp, whereas adjusting it even a hair too close makes the sound harsh and distorted in fff.”

My question is: how exactly does the presence of this escapement/let off position improve soft playing? Put another way, if a digital piano doesn’t have this tactile bump that comes with escapement, why is it more then more difficult to play softly? As a longtime pianist, I can’t seem to articulate why this is.

Is it because the presence of the jack allows the key to be controlling the hammer for as long as possible - therefore, the longer the key is directly controlling the hammer, the more control you have? In this case, why wouldn’t digital pianos set aftertouch equal to zero? Here, you’d have the entire key dip to control the “hammer”, which would maximize control. Since there’s no jack to reset in a digital piano, they wouldn’t have to worry about physically preparing the action for escapement - just sense when the key rises a few millimeters, then get ready for another keystroke.

I realize that the jack escaping is what prevents the hammer from jamming against the string, and that its quick return under the knuckle is what enables fast repetition, but none of those aspects of the jack seem related to how feeling that increased resistance when escapement happens makes it easier to play softly.

Am I missing something here? Thanks for the insight.

It's not that escapement gives the control... it's escapement at the last possible moment.
Just like it says--the more contact time between jack and hammershank the greater the control


Or, to think of the opposite...
If escapement happens at the beginning of the keystroke there will be zero control.

Do you find it just as easy to control your soft playing on a digital piano that lacks the increase in resistance that comes with the jack sliding out from under the knuckle?

I suppose my point is that there seems to be something about that change in the feeling of the key at let off that makes it feel more in-control, and this is why many digital pianos try to simulate this.

The closer the hammer is carried to the string before it escapes, the softer you can play, as the momentum of the hammer only has to carry it a couple of mm.

Without an escapement, if the hammer does not block against the string (like a clavichord tangent) and mute it, it will bounce against whatever pushes it towards the string, causing multiple strikes if it is pushed too close. So the escapement allows the hammer to be pushed closer to the string, and then fall back farther than it had been pushed, which in turn allows the hammer to be checked away from the string so it does not bounce or bobble.

Being able to be pushed closer to the string allows you to play softer more reliably.

Okay, I think I'm getting it now...

If the jack escapes very far away from the string, then you'll have to put a lot more energy into the key to give the hammer enough momentum to not only fly up towards the string, but then also strike the string with sufficient velocity - this additional momentum calculation sounds very difficult to do in the moment.

On the other hand, if escapement happens close to the string, then we can say that the velocity of the hammer when it lost contact with the jack will be roughly equal to the velocity with which it strikes the string, which sounds a lot easier than figuring out how much extra momentum the hammer will need to even make its way up to the hammer. In this way, escaping as close to the string as possible (without jamming, mind you) makes it easier to control the velocity of the hammer, and therefore soft playing.

Based on this, I'm guessing that that point of increased resistance you feel when escapement happens serves to tell the pianist when they should have finalized their velocity. In other words, if we're unable to feel when escapement happens, then we're left guessing where in the key travel our hammer velocity should be finalized, as that's the velocity that it will have when it loses contact with the jack.

Does that sound right to people?

Even with the closest possible let off there must be enough aftertouch or double bounce will happen.
Other factors too like repetition lever height and spring tension, friction in moving parts.
If letoff is too close there is the sensation of the hammer hitting string simultaneous or just prior to letoff.
I have a Horowitz recording live in Moscow and if you listen carefully it sounds like he likes letoff too close but there is no double striking.
Suggests there is a range of preference that works.

This is a good thing to consider. I also liked the point about the sensation of the hammer hitting the string simultaneously (or even feeling like it precedes letoff). I've felt that before and it can be quite jarring - I guess I'm just not used to it like Horowitz

Horowitz was unique in regard to his letoff setting, much closer than I have set it working for many world class artists. Never worked for him.
But he was a master of control for all dynamic ranges.

Checking also plays an important roll. The typical checking assembly is usually ok but for the actions where I have installed the WNG checking system - this includes specific hammer tail shaping and mating to the check, checking can actually be set at letoff if desired.
When I did this it gives another dimension of control that standard checking does not have.
A very unique feel.

The lack of ppp is more about control. Think of it this way. If you play a ppp blow on a piano with too much letoff distance you will get NO SOUND AT ALL. The hammer goes up/forward, the jack trips out, the hammer continues for a couple milimeters, stops, and falls back without even touching the string. So to play pianissimo notes you need to be playing a very precise mezzo piano with your fingers. Very precise because if you play too softly you won't get any sound at all and too hard and you won't be playing pp anymore. And there willl likely be greater variation from note to note. It's much easier to just have a regulated piano that consistently plays softly when you play the keys softly.

On several of Glenn Gould's recordings you can hear the hammer bouncing against the strings. He also had set off adjusted too close for most people.
Nick

I’ll add one more: voicing.
If the hammer will not give a warmer softer tone at ppp then your fingers will try to compensate.

I helped the performance venue acquire a Sauter upright.
It has the double escapement action.
It went into the artist dressing room for warm up.
Nothing but complements.
The touch and repetition is similar enough to a grand that it serves the purpose for warm up.
Imho one of the best uprights made.

It does NOT, it's exactly the opposite, it hinders for ppp playing. For ppp playing you want this distance as small as possible.

>Every millimeter of additional distance from the strings significantly compromises control in ppp, whereas adjusting it even a hair too close makes the sound harsh and distorted in fff.”

Greetings,
The let-off distance is the amount of space through which the pianist has to throw the hammer to contact the string. The point of escapement marks the moment that control ends. The smaller the dead zone that must be crossed, the less distance to be judged by the pianist. With just the right amount of force, a hammer can cross a 1/2" let-off distance and arrive at the string with just enough force to sound, but that right amount is going to be difficult to judge. If there is a 1/16" gap that must be crossed, judgement of the amount of force needed for a given level of play is much easier. An analogy is trying to pitch pennies as close as possible to a wall, much more difficult from three feet than from from 2 inches.

Too close and the hammer can be trapped between the vibrating string, (in motion, strings are not a fixed height, as their vibration requires an excursion zone). The excursion zone is far greater on the lower bass strings than it is on the upper ones, hence, let-off needs to be greater in the bass. Without sufficient clearance, fast repetition can cause the bass hammer to contact the string at the string's lower limit of the zone while still impelled by the jack, resulting in broken shanks or horrible tone. Ideally, let-off would taper on a per note basis from bottom to top, but a consistent setting is more practical. The additional momentum found in the heavier bass hammers offsets the greater let-off needed, to a degree.

A critical aspect of let-off is the consistency from note to note, since the pianist's touch sensitivity can quickly adapt to whatever the let-off distance is, as long as there is only one. Nothing interferes more with careful voicing of chords and control of pianissimo passage work than having disparate notes requiring differing levels of force to sound evenly. Other factors, such as when the drop screws are contacted, spring strength, jack position, friction in the shank centers, and even damper timing, can cause inconsistency of resistance, but let-off tends to be the main contributing dimension to the ability of control at ppp levels.
Regards,

This is the conclusion that I was reaching - contrary to what I initially assumed before I had learned anything about how the action worked!



Ed, that was a great explanation. I appreciated the extra details on the greater let-off required in the bass - I had never before considered why that was. Thanks for the in-depth reply.

This is my first thread on this forum, and I'm blown away by the responses I've gotten - just what I was looking for. Thanks, everybody!

Most pieces of piano music require you to play more than one note at a time and many times the succession of the notes is rather quick. This means that whatever dynamic you require of any particular note is best achieved rather quickly in terms of the effort and distance the finger is moving if you want to feel in control of the dynamics and secure in being able to place the whole sequence of notes in the desired order and dynamics.

Just studying how one note plays in isolation will not give you this information if you don't account for the minimum key speed required to reliably produce a soft sound.

What I am driving at is the mechanical timings of events in the action cycle are not sufficient information to assess dynamic control. You need to know something about the inertial response of the hammer in relation to the key movement.

It can be demonstrated that actions with well proportioned inertial properties are decidedly insensitive to escapement distances as regards soft control.

In vertical actions there is often issues with the center of gravity of the hammer assembly that cause bobbling hammers in the tenor section above the overstrung section.

Another point no one has mentioned is that the 'letoff resistance' that is felt in many digital piano actions is not put there to improve the touch, or help with control. It is put there to make the digital action feel a little more like an acoustic piano action.

Same with the graduated touch resistance in digital pianos - it has no real benefit to the performance except to make the digital action feel more like an acoustic action.

These "feels like" features help a little for pianists who must move from one type of piano to the other, but that's about it.

If I am not mistaken, very early fortepiano actions had no escapement, and the pianist had to learn how to develop the "touch" so as to not jam or bobble the hammers against the strings.

Peter Grey Piano Doctor