I take issue a little bit with the comment by the editor to the 
effect that "One camp of rebuilders restores the instrument to new 
or better condition, whereas the other camp repairs the instrument to
less-than-perfect condition because the owner can't afford a complete
restoration.  Only a Duo-Art in new condition can play a 3-note chord
at zero level.  What should the player tech tell the customer?"

While the first sentence about the quality and thoroughness of
restoration varying widely among rebuilders and customers is entirely
correct, the second sentence linking the quality of the rebuild to the
ability of an instrument to play a 3-note chord at zero level is not.

More accurate would be to say that "Only an improperly adjusted Duo-Art
will consistently play a 3-note chord at zero level."  And while it is
desirable to have a totally airtight stack, with sealed interior wood
surfaces, etc. (I rebuild mine so that I can play it for several seconds 
with mouth suction on one inhale), that actually has almost nothing to
do with the instrument's ability to play low-intensity chords in a
controlled way.

The Duo-Art test roll is set up so that at various power levels, it
checks that some chords with fewer notes play (i.e., it is loud enough)
and other chords with more notes don't play (i.e., if they play, it 
is adjusted too loud).  Specifically, level zero Accomp. should play
single notes with the damper lifted, be borderline on single notes 
with the dampers not lifted, and fail to play with two or more notes
(including 3 notes with the dampers not lifted as coded on Bernt's
customer's roll).  Level 1 Accomp. should play 3 notes, but not 5 with
the dampers lifted, etc.  All of this shifts somewhat as the tempo and
air usage of the wind motor changes, or if the Theme intensities are
coded so that the expression box spill valve begins to close.

But there is a natural tendency for many rebuilders to adjust things
too loud to compensate for uneven action weighting or friction problems, 
improperly coded rolls, and the tendency of customers to complain more
if notes don't play than if the instrument fails to provide the
controlled, nuanced soft playing that it was designed to provide.  

So I suspect many Duo-Arts are adjusted so that the three-note
zero-level Accompaniment chord plays at least a little bit, with the
trade-off that they are unable to play single pianissimo notes
sufficiently softly.  But it is much better marketing to attribute the
overly-loud volume in quiet passages to "my high-quality airtight
rebuilding job."

And even a fairly leaky stack will be able to play soft notes and chords 
well, if the action is evenly adjusted and the Duo-Art zero-level
setting is adjusted properly to compensate for the leaking, since the
pump is already dealing with a much larger intentional leak from the
spill valve, which is wide open at zero level.  Where the tight stack
makes a difference is with loud chords with many, fast repeated notes,
with the tighter stack playing all the notes at sustained volume and
with the leaky stack audibly beginning to lose power.

Ralph Nielsen
http://www.historicpianos.com/