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I'm a relative beginner here, and do not know what people refer to when they speak of "aftertouch" and adjusting it.

What is it?

You want to post in the Digital Pianos - Synths & Keyboards forum. Aftertouch is something more expensive DP's have to control certain features.

They try to put it in those "more expensive" DP things because acoustic pianos have it, most notably grands.

As for what it is.... Even my instructor at the Yamaha Piano Academy couldn't give a definitive answer on that. Different people will describe it differently, and they'll all be right. It's what you feel in the last bit of the key stroke.

Cheers,
Greg

Aftertouch is the distance between let-off and the bottom of the key stroke.

To feel aftertouch, slowly depress 1 key until you feel the friction or "bump" where the jack hits the letoff button, and rotates out from under the knuckle.

Go very slowly, using your sense of touch. After touch is the distance the key travels AFTER this "bump".

After touch plays a very important role in the overall touch of a piano. Too little aftertouch and the action will feel hard and hammers might block on the strings. Too much aftertouch and the action will feel mushy, and the key may block AFTER striking.

JR,

I can't define it, but I can tell you three ways it has been referred to in my experience. I think a part of the problem is that some uses of the term 'aftertouch' relate to key velocity while others relate to key pressure.

First,I have two acoustics. One of them allows me to play at a very soft volume easily. When I slow my attack velocity on the key, the key resists evenly from the first impact to the point where the key bottoms out. This even key response assists my efforts to play at a soft volume. The other piano had a tendency after initial resistance at the top of the keystroke to then go 'plop' to the bottom. This impeded my efforts to play at a soft level. When my tech was around for tuning, I mentioned this to him. He told me it was an aftertouch problem. He adjusted the regulation on the piano that had a tendency to 'plop' so that it became marginally better, but the other piano is still superior (probably by design).

Another instance it came up for me was with teachers. I had a couple who stressed to me the importance of working on MY aftertouch. In this instance they wanted me to exert different levels of pressure (not velocity) on the keys after they bottomed out. Obviously, this can only occur when your fingers are not moving quickly from key to key. These teachers believed that the level of pressure applied to the key after it bottomed could affect not only the decay, but the quality of tone production. I don't know if it's myth or reality, but I'm easy to fool so I have come to believe it's true (at least on some pianos)

The last instance is with digitals. In digitals, the attack velocity isn't all that important because you are dealing with a fairly narrow dynamic range. If you attempt to attack with great velocity to achieve a big fortissimo, all you will get for your effort is a hard unpleasant bottoming out which feeds back through your fingers. The sensors won't care what you do beyond their loudest volume sensitivity. Conversely, if you attempt to play very softly with an attack that caresses rather than strikes, you will waste your time since the sensor response will not differ beyond its lowest volume option.

OTOH, pressure on the keys of a digital AFTER bottoming can be significant. You can hold a key in bottom position and change the volume simply by exerting different levels of pressure. This has nothing to do with velocity. For example, let's say you are using a string pad sample on a digital. You can create the illusion of a string ensemble that is playing a note softly, building the same sustained note to a crescendo, and gradually fading the same note to a pianissimo without moving your finger -- simply by applying different levels of pressure to the key while it is at bottom position. In the digital world, this is usually referred to as aftertouch.

Acoustic pianos don't have it (unless you're a piano technician). Check turandot's post above on DP's.

Sure they do, even if we're apparently talking about different things. BDB and BoseEric's responses explain it.

Steven

Thanks, everyone. I must say that I see exactly what BoseEric talked about on my Kawai upright. With the front panel off, I can see and feel that point where the jack comes out from under the knuckle. Thanks for the info.

I believe that better digital pianos with weighted keys have a rubber strip (or equivalent elastomeric means) for braking the keys when they bottom out. It is a completely different feel from the aftertouch of an acoustic.

In a digital piano, further pushing on the rubber can be used to produce additional sound effects, as stated.

With regard to acoustic pianos, there are endless religious warfares on the sound effect of the aftertouch.

Aftertouch is the region where the key has no mechanical connection to the hammer. It can have no effect on the sound.

That's why it's religious...ya just gotta believe!!

So is the letoff setting directly related to aftertouch? I think that letoff is the amount of distance the hammer is from the string when the jack rotates and the hammer uses it's momentum to continue to the string, as it is no longer being pushed towards the sting. So I am trying to understand the difference in these terms. Thanks

Aftertouch is also a function of the key dip. Like so many adjustments in the piano, there are a number of adjustments that must be correct in order to get it right.

Striking distance (or hammer blow) and hammer drop are important too, but as BDB said, there's lots of things that go into the whole aftertouch experience.

Cheers,
Greg

Does this mean that is there is no sensation in the fingers of the hammer striking the keys? As a practical matter, if I were to install a MIDI strip and stop-rail for silent practice, would the effect of the after-touch render the feeling of the keyboard unchanged?

The hammers do not strike the keys.

Are you sure BDB? I thought that was the cause of the chipped ivories I see on so many pianos...

BDB, I'm sorry, I wrote "keys" instead of "strings". It was late. Since you said earlier that "aftertouch is the region where the key has no mechanical connection with the hammer", can I conclude that my fingers will be unable to tell the difference between the hammers hitting the strings or hitting the stop-rail?

I'm not sure this is true. It's like saying that the follow through in a tennis stroke has nothing to do with what happens to the ball because after the ball leaves the strings its not affected by the racket's motion.

The point is that the follow through(after the ball has left the strings)is determined to a large extent by the motion of the racket before the ball hits the strings.

I would say the same is true in piano playing. The motion of the finger before the aftertouch motion of the key(which effects sound) affects the motion of the finger during the aftertouch portion of the key motion.