While the subject of Duo-Art soft playing is still fresh I would like
to bring up another factor that can cause notes to skip at low vacuum
levels -- the soft or half blow pedal in upright pianos.  The use of
the soft pedal in uprights introduces significant "lost motion" into
the piano action.  This in turn leads to notes missing at low vacuum
levels.  Over the last 30 years a lot of discussion has taken place
about this and how to overcome the problem.  Some "restorers" have even
added a fifth Duo Art expression accordion to open when the soft pedal
is on.

After the recent correspondence on bleeding air into the stack to
modify the low end vacuum levels it has occurred to me that this may be
a possible solution to the soft pedal problem.  --simply close of this
air bleed when the soft pedal is on.  Alternatively you might bleed in
a small amount of controlled vacuum when the load pedal is on.

I have not actually tried either of these approaches but I put them
forward for comments.

Phil Dayson