Help with Upright Steinway Sostenuto

Israel Stein
Sun Aug 10 10:19 MDT 1997


Steinway publishes a technical bulletin. The section on upright sostenuto
regulation is quite thorough and helpful. It is Steineway Technical
Bulletin Volume II #1. It applies to all current upright models - K-52,
1098, 45 - and both types of upright sostenuto - felt and neoprene tabs.
Sounds like you have the felt tab model. I've used the method in the
Steinway bulletin back when I worked full time for the Boston Steinway
dealer, and we got occasional mis-regulated sostenutos delivered. (No piano
was sold or even shown to anyone until the shop gave it a clean bill of
health. This dealer takes his prep and service obligations quite

Briefly, the idea is to regulate all sostenuto tabs in as straight a line
as possible both vertically (by screwing them in and out) and in the
backward-forward plane (by bending the wires). This adjustment is done on
the bench, with the damper lift rod wedged up so that the dampers are
approximately in the position they are when sitting on the strings.
Needless to say, the dampers need to be in pretty good regulatiuon (both to
key and to pedal) for this to work. 

You then put the action in the piano, and adjust the position of the
sostenuto rod and its rise so that it functions properly. You remove keys
#3, 26 and 49 before replacing the action in the piano, so you can see what
you are doing in the most strategic places. Use keys #2, 25 and 48 as your
guide keys. Now, some specs:

The sostenuto rod lip at rest should be at about 40 degrees pointing upward
towards the wippen flange pin. Adjust this by shortening or lengthening the
connector rod from the trap lever to the sostenuto rod - it has threads and
nuts for this.

The lip of the rod should be 1/16" below the felt tabs. Adjust it by
shimming the rod brackets up and down on the keybed. 

Looking at your test keys, make sure that the rod lip engages the tab on
the keys by a minimum of 1/32". If not, adjust the position of the rod back
to front or up and down as needed.

Now, try the sostenuto on each key individually. If some don't work, you'll
need to adjust their tabs individually on the bench, by trial and error. 

Adjust the amount of damper rise with sostenuto by moving the (sostenuto
rod) brackets backwards and forwards. 

That's a synopsis. Call Steinway Tech Services and get the bulletin. In
fact, get all of them - they should have plenty on various topics. If you
are going to be getting referrals from a Steinway dealer who doesn't give
you any backup, no sense making yourself look bad. New Steinways do need a
lot of prep (I spent close to 2 years doing it for a dealer who did back us
100% - even when Steinway disagreed!
Oh, about your squeaky sostenuto rod teflon bushing - I came accross a few
of those. Sometimes the bushing can be damaged - Steinway sells
replacements, and the replacement is quiet. Sometimes, the bracket is too
tight (sounds like you did that when you bent it). Just throw away the
teflon and replace it with good ol' bushing cloth. It works just fine...

Israel Stein, RPT