[CAUT] sostenuto

[Fred Sturm]

I agree with Jon Page about using a flashlight that gets down between  
the strings and lights the tabs and sostenuto rod directly. I have a  
little more elaborate method of evaluating without removing the  
action, and that really doesn't take very long.
1) With flashlight well placed, raise the dampers (press the pedal)  
just enough so that the tabs are even with the sostenuto rod at rest,  
IOW even with the round part of the rod. Get your eye vertical over  
the gap between the tabs and rod and look at the gap (move the  
flashlight from section to section). Is the gap sufficient (so that  
there won't be occasional "hangers"), but minimal, about 1-1.5 mm? Is  
the gap even? This tells you a lot about the in/out position of the  
rod, and about the evenness of the line of tabs in that plane. Tabs  
that are obviously out of line can be slightly adjusted from above  
(without removing the stack), with judicious use of a slim bladed  
screwdriver, pressed against the bottom of the wire/top of the top  
flange.
2) Again looking at in/out position of the sostenuto rod, but also at  
whether the sostenuto pedal is well adjusted, with damper pedal at  
rest, depress the sostenuto pedal fully. Observe with flashlight. Is  
the blade horizontal or nearly so? How much does it overlap the tabs?  
Get a second perspective by first depressing the damper pedal, then  
the sostenuto pedal. How much does the blade overlap the tabs?. Does  
it raise the dampers the same as the damper pedal? more? less? This  
can lead you to whether you need to take up lost motion, adjust the  
stop felt, and tell you about in/out position.
3) Investigating sostenuto rod height relative to tabs: The first step  
is what Kent mentioned, being sure the blade doesn't brush tabs of  
dampers at rest. But you can learn more. Press the damper pedal a very  
slight bit, and work the sostenuto pedal. FInd out how much you need  
to lift the dampers with the damper pedal before the blade starts  
catching against tabs. THere should be a little bit of safety factor,  
but very little. Then work backwards from the top. Damper pedal fully  
depressed, press the sostenuto. It should catch all. Damper pedal not  
quite fully depressed, press the sostenuto pedal. FInd how much safety  
factor there is in this direction. In any of these tests, you don't  
want to jam on the sostenuto pedal, just a light touch to see when and  
where you get rubbing contact, or from above, when there starts to be  
jamming. This can also tell you what sections might be different from  
others (which sections catch first from below, which from above), all  
of which tells you where you might want to raise or lower the rod. And  
it tells you how even the tab line is horizontally, if there are  
several that behave markedly differently from the others (catch much  
earlier, while the others are missed).
4) It's a good idea to note whether dampers are lifted the same from  
the keys as from the pedal. If there is late timing, and the dampers  
lift less from the keys, you may run into trouble of dampers not  
catching consistently.
5) The Steinway rod can be adjusted with action in to a large extent,  
except raising the rod. You can usually get at the screws and loosen  
them enough to jar the rod forward or backward a bit, then tighten and  
try again. And you can tap downwards to bend the brass brackets to  
lower the rod.
	I find that this approach tells me all I need to know, and that I can  
predict if there will be any problems with dampers passing on hard  
blows, or not being caught.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



On Feb 1, 2008, at 10:07 AM, Kent Swafford wrote:

> What are all the procedures for making certain that the sostenuto  
> mechanism is ready for concert use? Here is what I have come up with  
> so far.
>
>
> Dampers must be in good regulation, and all dampers must seat  
> properly. The damper upstop rail must be regulated perfectly.
>
> Depress damper pedal. While continuing to hold the damper pedal,  
> depress the sostenuto pedal. While continuing to hold down the  
> sostenuto pedal down, release the damper pedal. All dampers should  
> remain raised. (This is a more severe test than depressing each key,  
> then depressing the sostenuto pedal, and releasing the key to see  
> that the damper stays raised.)
>
> Depess sostenuto pedal. While continuing to hold the sostenuto pedal  
> down, depress the damper pedal. While continuing to hold the damper  
> pedal down, release the sostenuto pedal. The immediate flipping of  
> tabs should make a noticeable sound as the blade returns to its rest  
> position. (If the blade is held too tightly in its mounting  
> brackets, there might be an inappropriate delay in the return of the  
> blade to its rest position. The tabs should not be able to keep the  
> blade from returning to its rest position.)
>
> Depress and release the damper pedal. Depress the sostenuto pedal;  
> no dampers should rise. In addition, there should be no noise  
> resulting from slight contact between the blades and the tabs of any  
> dampers. (If noise is heard from the blade contacting tabs as the  
> sostenuto pedal is depressed, you may need to rest your finger on  
> each damper in succession while depressing the sostenuto pedal to  
> find the damper tabs that are makding contact with the blade.)
>
> Depress and continue to hold down the sostenuto pedal. Deliver a  
> double-forte blow to every note that has a damper. All dampers must  
> return to their rest positions on the strings as each note is  
> released. (This is a particularly severe test. This test may fail if  
> the sostenuto pedal is not depressed as far as is possible.)
>
> It appears to me that delivering double-forte blows to notes when  
> the sostenuto pedal is depressed and expecting them not to sustain  
> is at the limit of what can be expected from the sostenuto  
> mechanism. I think it's OK to instruct pianists that they must be  
> certain that the sostenuto pedal is depressed as far as possible if  
> they expect double-forte notes not to sustain when the sostenuto  
> pedal is down.
>
>
> Comments? You'll notice I haven't mentioned how to regulate the  
> blade and tabs. These are just the tests to determine whether I'm  
> done, that is, whether further regulation to the balde and tabs are  
> necessary.
>
>
> Kent Swafford
>