What can I request regarding tuning and intonation?

The highs are becoming more crescendos......I heard a new one. I would say that the concepts are much more refined, for example the last high notes result in a bit of a crescendo... but not to my ear... opp. wider octaves can be played etc... But it must be evaluated from instrument to instrument. The C3 has a good balance between lows and highs, although I find all Yamaha models difficult to tune. The bridge is a bit "increased" to give more power, but in some areas this can translate into disharmony. The tuner must be very precise with the key movements, because the positions of the pins have little tolerance for error. these are just some observations that come to mind.

A good tuner knows how to make a tuning brilliant and cantabile; if it were that easy to explain in a few words, I would say that this time experience wins. Voicing is something else. It consists of returning to the hammer that right timbre and sonic balance that it may have lost from striking the string for a long time. In the hammer, there are zones diversified in terms of hardness and elasticity, and this changes as we go through all the sounds of the keyboard. One uses a voicing tool, an instrument composed of a handle and a series of needles that can range from 1 to 5, to prick the felt zones more or less deeply and separate the fibers from each other. A difficult and irreversible intervention, it can grant a hammer group an exceptional sonic quality... as it can kill it. Good voicing and good hammer construction should provide a clear pianissimo and a round fortissimo and reveal, moving from one extreme to the other of sound intensity, a different timbral progressivity (that is, a rich quality of harmonics).

Yes, I know what tuning consists of. I wanted to ask how these interventions can (and if they can) be customized, in what way and with what limits. People often talk about customizing the action, but never about tuning and voicing.

It is true that few texts explain it, and they cannot always be exhaustive. In fact, from hammer to hammer, the voicing intervention can vary greatly, especially if one is faced with hammers already pre-voiced by the Manufacturer. Regarding tuning, there are precise theoretical rules, which however can be modified depending on the disharmonies of the instrument.