Recent MMD postings about Duo-Art soft pedal mechanisms have not
mentioned the fact that some Duo-Art grands have only a keybed shift
for soft pedal operation, without any provision for hammer-rail lift.
My own c.1926 Steinway grand is so equipped.  This instrument is a
Spanish art case Style O.R., Serial No. 239971.  In most respects its
configuration resembles a more or less typical post-1925 Duo-Art, with
tubing passing between keys, crash valve expression system, and a
pneumatic installation of the sort one might expect to find in a Duo-
Art grand of that vintage.  The piano action, however, has no provision
for hammer rail lift, and obviously never did.  Except for extended
keys, the piano action more closely resembles that of a non-reproducing
Steinway grand.

Performance wise, the keybed shift offers advantages, a very important
one being that lost motion does not occur between the poppets and
their corresponding felt blocks at the rear of each key.  Lost motion
is frequently associated with dropped notes and uneven playing.  The
lateral movement of keys during soft pedal operation is never
problematical, if everything is properly adjusted.  There is no
evidence of any abnormal wear pattern in the hammers of this piano
after several years of playing.  The potential for uneven hammer wear
is, of course, inherently minimized by the fact that soft playing tends
to be coded at low intensities, keeping hammer wear in the una corda
position minimal.

There is no reason why the keybed shift cannot provide excellent
results when playing Duo-Art rolls.  On the down side, the degree of
softening cannot be adjusted as can be done with a hammer-rail lift.
However, the amount by which musicality might be enhanced by such an
adjustment is debatable.  If a keybed shift were used to obtain soft
pedal information during recording sessions, then a hammer-rail lift
would need to be set to emulate the result of a keybed shift.  Beyond
that, such adjustability would offer no particular advantage.

Dave Saul