I should preface that this is not a question, but rather a reflection for discussion.
It is said that the spring tension must guarantee the hammer a decisive movement from the let-off point to the escapement without wobbling. In an American forum, however, someone claimed that the right tension is the one that prevents bobbling during a pianissimo touch.
I believe that such adjustment is the most customizable one and does not affect other adjustments; on the contrary, it is the tension itself that depends on the pre-regulation, the regulation, and any potential friction.
The tension I prefer is the one that allows me to play, after depressing the key down to the escapement point, with a small tap—almost like a finger pizzicato—and hear a very faint sound. No more! Otherwise, the tap can be heard upon the key's return and, paradoxically, repetition becomes more difficult for me (I am not generalizing, I am speaking for myself). However, the vivacity of the hammer's return on the escapement screw is not very lively (a technician told me it should be like a clock hand). In this way, however, I feel a harder keyboard and a sound that is indeed more decisive, but less elastic. With the tension I described, it is easy for me to play on the escapement without compromising the fundamental sensation of the key or the feeling of "playing too much on the surface." Perhaps this is due to my technique or my approach to the instrument. Others speak of improved repetition with higher tension. All of this also takes into account the height of the repetition lever relative to the upright/post. With less tension (the one I described), I tend to play with very arched fingers (I previously mentioned pizzicato) and a firm, "digital" technique, whereas with higher tension, I find it spontaneous to rest my fingertips a bit more and help myself with the wrist and lateral movement of the elbows, almost as if wanting to sway and play on the surface.
What do you think? I have illustrated both technical-mechanical and technical-musical aspects.
A technical question now: are there differences when adjusting the tension from the two sides of the spring—the one going to the repetition lever and the other going to the post? On my instrument, there is a specific screw for its adjustment, so there is no need to adjust the spring directly by displacing it and using the appropriate tool.
