When you keep the F key pressed, doesn't the damper from that key stay up until you let go of it? (about the same effect as the sostenuto pedal) Shouldn't that make the same effect as the pedal for that key?How does the sound get longer with the pedal than just with the key?
I not a technician (though I would like to be someday) but my understanding of what the damper pedal does is adds a sort of extended sound to the note. On my piano when I play above where there are damper's on my piano the pedal still has an effect on the note when played. It would seem that the pedal has some sort of added acoustical effect besides the damper. (perhaps all the dampers being lifted up?) So, yess the damper does stay up. No it does not seem to me to have the same effect as the pedal. Does this answer your question?