In answer to Chris Morgan's suggestion about bleeding a small amount of
air into the stack to adjust the minimum stack vacuum -- the idea works
wonderfully well.  I have been doing it for about ten years on my
Duo-Art.  Duo-Art rolls are highly variable in the minimum vacuum level
required for them to play softly.  This is a simple way of overcoming
the problem.

Here are a few extra hints and comments.  You need two bleeds, one for
each half of the stack.  The bleed must be fitted somewhere between the
output of the expression box and the input to the stack.  A good place
is on the rubber connecting hoses.

On my system I did not use needle type valves but made up two slide
type valves, each one with 5 holes of about 1/32-inch diameter each.
By moving the slide you can progressively increase the bleed from no
holes up to five holes.  The system is reproducible -- all of my rolls
have been tested and have been labeled with the required bleed level
for minimum volume playing .

The five bleed holes give an adjustment of approx. 2" vacuum at the zero
expression level, enough to cope with any roll variability.  As the
expression level increases the bleed has smaller and smaller effect
until at level 16 the vacuum level is virtually the same whether or not
the bleed is in place.  The theme vacuum remains higher than the
accompaniment vacuum at all levels.

I'm sure I will get my share of criticism for this "unauthorized"
modification.  I feel however that this is a simple solution to a real
and a complex problem.

Phil Dayson

 [ A Doer makes things happen, a Naysayer criticizes.  MMD encourages
 [ the former.  You own the piano, you can do anything you wish.  Go
 [ for it: have fun experimenting, and enjoy the fruits of your efforts!
 [ -- Robbie