Hi - first I will like to thanks all for such a wonderful forums. I got up to this point on this circuit thanks to many of you.
At this point the attach circuit behavior is almost what I need. The idea is to hit the piezo sensor, a soft hit will make the electronic switches in turn with a long delay. A hard hit will turn the electronic switches at the same time. This is connected to the inwards of a MIDI keyboard , it generate MIDI noted with a "velocity" value based on how hard I hit the piezo.
My next step, this is where I need some help, is to calibrate the circuit to operate better. I mark the areas of the circuit were I had find that changes (in the resistance) change the behavior of the circuit. Any suggestion on how to improve the circuit? (I need it to have more sensitivity to the hit of the piezo - It is right now mounted under a piece of wood "like a xylophone bar")
Thanks