On a real piano, sostenuto holds the dampers off the strings when either keys are pressed or the sustain pedal is pressed (effectively holding all dampers off the strings). But on DPs and in Pianoteq, the sostenuto doesn't hold the [imaginary] dampers when the sustain pedal is pressed. I realized this when I went to play one of my own pieces on an acoustic and had the unpleasant surprise of all notes being held by the sostenuto pedal when I thought it'd only hold a few.
To the developers: could you make Pianoteq respond to sustain-sostenuto as on an acoustic?
Ahhh!!! Are you aware that the sostenuto pedal works different ways on different pianos???
The "true" way a sostenuto pedal is supposed to work only functions correctly in decent grand pianos ... and Pianoteq. Please note that the sostenuto pedal does not function this way in most bottom-of-the-line models of grands -- and essentially never in uprights!
Your opening sentence (about the sostenuto pedal holding dampers off the strings) -- and through no fault of your own -- demonstrates that you observed the workings of either an upright piano or a lower-end grand piano. This is NOT the true function of a sostenuto pedal ... which Pianoteq does model correctly. Please do not be offended: I am not putting you down ... you correctly described what you saw, except that the piano you described -- does not contain a middle pedal that functions as a true sostenuto.
In the better grand pianos, if you were to press the sostenuto pedal (with no notes held) and look at the dampers ... and would see nothing happen! Similarly, if you were to depress the true sostenuto pedal, and THEN play some notes ... none of those notes would be sustained! This is because grand pianos with working sostenutos contain a strip of metal running the width of the piano (incidentally, called a "monkey bar") that actually slip beneath the damper rods of those notes that are held just BEFORE pressing the pedal. The monkey bar (which slips below those held notes' raised dampers) then proceeds to hold only those held notes' raised dampers after you have lifted your hands off the keys.
The true action of a sostenuto pedal is comparatively expensive, and effectively answers walk-in customer's question, "Why does this 4'11" piano cost $10,000 and yet this 5'3" piano cost $14,000? Are you telling me that a 4" longer piano of the same brand costs an extra $4,000?"
A partial answer to the walk-in customer's dilemma is that the smallest 4'11" piano in the store is not equipped with a true sostenuto action. In its place, the middle pedal simply lifts the lowest ~1-3/4 octaves' dampers as a group -- even when no notes are held beforehand.
In the case of essentially all uprights, the middle pedal (incorrectly called a sostenuto pedal, because it cheats and does the same thing as a lowest-end grand) only functions to move the lowest ~1-3/4 octaves' dampers as a group. Since this is not a true sostenuto pedal action, some Pacific-rim piano manufacturers add a second function to the middle pedal -- it's called a "practice pedal", because the middle pedal can engage a strip of felt that swings in between the strings and the hammers and act to mute the whole sound of the piano.
* * * * * *
Now, what happens to the sound when either an upright piano or a low-end grand's middle pedal is engaged, if it only raises the lowest ~1-3/4 octaves' dampers???
Because all of the lowest ~1-3/4 octaves' dampers are released, those strings are free to vibrate in all of their sympathetic vibrational modes when ANY other notes are played, the effect is to muddy up the sound. Of course, the originally justified reason for this pseudo-sostenuto pedal was to keep the bass notes sounding and supposedly leave the rest of the piano's notes quiet -- this simply does not happen.
In contrast, a true sostenuto sound of a good grand piano will only allow those intended notes to sound -- assuming the pianist knew how to pedal correctly with the sostenuto.
Enough of my rambling for now,
[EDIT: Added the following postscript to the thread:]
P.S. That Joe guy has much too much time on his hands!
Last edited by jcfelice88keys (02-07-2011 20:31)