high piano keys too light

It is normal for it to be lighter towards the treble, perhaps not in an absolute sense (grams of force) but as a sensation, given the lower inertia. Anyway, check if there are any weights on the key in the front part (towards the pianist, I mean); if there are, you can eventually remove a few grams from the front to gain weight on the key descent, provided that the excessive lightness is not also due to the fact that the pins have loosened over time, especially those of the hammer rail. In this regard, verify that, by slightly oscillating the hammer laterally with a finger, the pin is stable and that, by unscrewing one, the rails remain suspended when you hold the hammer in your hand, without falling down under their own weight.

I assumed it is a grand piano; if instead it is an upright, after checking the nut forking, a weight can eventually be added to the rear part of the key. In this case, the damper springs also contribute to the total resistance against the key descent, depending on their point of intervention, more or less delayed, so it is clear that where they are missing one can feel a slight difference; even if the absolute value of the descent weight is the same, one will never manage to obtain a uniform response because weight force is different from elastic force: on a grand piano there are only weights to pull up, while on an upright there are also springs to compress, in addition to the uncontrollability of a hammer thrown towards the strings and not accompanied...

it's an upright, an old Chickering. Actually, there is a little bit of lateral play. what can be done?

Increase the pins.

In my opinion, in your words, enricofabio, I see two aspects of the "problem"... if we want to call it that. Premise: it is evident that the sensation of greater "responsiveness" of the action towards the treble is favored precisely by the lower inertia. Moving towards the treble, the key downward weight can decrease slightly and the return weight increases. This is not the case in the bass, where the action shows the greatest gap between the two weights. This is indeed due to the larger and heavier hammers which, even if balanced with greater key weight (lead weights), have greater inertia.

So first of all, eliminate excessive slowness or excessive resistance of the pins; check and make the smoothness of the action uniform (check the pins of the hammer shanks, the jack shanks, and the escapement wippens).

One practical way to avoid being forced to use measuring instruments for these resistances is, as I have already mentioned in other posts, to observe if the shank falls under its own screw weight. The shank must fall easily and uniformly. If the pin is too loose, check the lateral play of the stiletto, jack, or wippen, while holding the shanks firmly. A subsequent check, should such looseness not manifest itself, can be done by "rocking," for example, the hammer, suspending it by the shank with two fingers. It should not complete more than two to two and a half oscillations.

Another aspect of the problem, another perspective, can be evaluated from the standpoint of piano technique. While maintaining that the sensation of smoothness and efficiency on the keyboard is uniform, in my opinion, from a pianistic point of view, one should not alter the weights and leadings in an attempt to have a "heavier" keyboard to "practice" on and thinking of "strengthening one's fingers."

In my video tutorials on piano technique, I discuss this concept by stating that healthy technical development occurs through the understanding that muscles must be tension-free and gain energy from the participation of the entire muscular apparatus available to the pianist. Naturally, many difficult passages can and must be studied and worked on under the watchful eye of a good teacher, always keeping in mind, however, that the correct "gesture" precedes the acquisition of "muscular strength," which, anyway, without excessive gymnastic "torture," will become increasingly powerful and skillful. Furthermore, an excessive keyboard weight does not favor—on the contrary, it nullifies—the development of sensitivity and the search for various timbral-dynamic colors. This is why great brands, like the one your instrument belongs to, pride themselves on achieving a refined design (proportion of key length, jack-hammer position, action weights) that aims to reduce the downward weight relative to a good return weight. Therefore, I take the liberty of advising against varying the keyboard weighting except for minimal corrections due to the installation of a new hammer assembly (identical in weight and shape to the original one). In the event that the hammer assembly has been shaved, finally, the downward weights would have been slightly altered. But counterbalancing them at the rear of the keys would be equivalent to altering the inertia and erasing (unless there is a written record) the reference to the original weighting.

A good technician will know how to evaluate all this and decide with you the necessary and most urgent interventions to make your instrument's performance satisfactory to you.

Happy Music

thanks Pianoexpert. I would also ask if it is unusual and inadvisable to change the distance of the hammer from the string in the various sections to have lighter bass or heavier treble. I am probably saying something nonsensical, but I tried out of curiosity and the sensation is not bad.

you can make many custom adjustments, but musically and technically it is not appropriate to distort the principles and stray too far from the standard regulation recommended by the Manufacturer. In any case, the hammer-string distance should as a rule be uniform across the sections. If necessary, slightly shorter in the treble to favor a more determined "snap" of the escapement lever (also a greater "aftertouch"). This also favors greater cantability and an easier jeu perlé