Hi Paolo, I just finished "enjoying" your fifth video on piano mechanics; I must tell you that you've answered some of my questions about mechanics, but one remains: as far as you know, has there ever been an attempt to implement double escapement on upright piano mechanics? Do you think it is possible?.
One last thing, is it true that double escapement helps a lot with the execution of trills?
But of course. Krauss invented a small repetition lever on some of his uprights. I don't know if they are still produced. I remember trying one, but it doesn't seem to me that there is much difference. Correct regulation is also important on the upright. It's not certain that trills work better on the grand. I would say that a well-conceived and somewhat studied trill (in the sense of understanding well how many notes there should be in relation to speed and how it must start and end) can be successful on both instruments