Upright Sostenuto

[Michael Spalding]

Listers:

Yesterday I serviced a Mason & Hamlin model 50 upright, ca. 1975.  The
owner is a piano teacher, this is her "private" piano, (she has a second
piano for teaching).  She complained that when the sostenuto pedal is down,
it is very difficult (i.e. a lot of resistance) to play the notes whose
dampers are not being held up by the sostenuto.  I pulled the action and
looked at the mechanism, and to me it looks like, by design, this thing
will never work.  The "tabs" are 1" pointed wires extending down from the
ends of the damper levers.   The "blade" is a thin rubber sheet held in an
aluminum channel which pivots mostly up and a little bit back (towards the
strings) to engage the tabs.   When the sostenuto blade is raised, any
dampers not already being supported by it will run into the blade before
the wippen reaches let-off, hence the "hard to play" complaint.  I'm sure
it's also putting a lot of stress oin the action centers.  My question(s): 
Can the M&H upright sostenuto be regulated to function correctly?  If so,
how?  Or was it just another bullet-point in the sales brochure and never
expected to work right?  Other manufactureres of quality pianos make
uprights with sostenutos, for example Kawai.  Does theirs work?  Is their
design different from the M&H?   Sorry I don't have photos to post.  Got to
start carrying the camera on tuning calls.

thanks,

Mike


Michael Spalding
spalding48@earthlink.net