The following comment from Robbie is good advice:

>[ A player tech told me that more than once he encountered a weird
>[ sounding Duo-Art and then discovered that it had been rebuilt
>[ without the bleeds at the accordion pneumatics.

It might clarify same to explain that the dynamic valve box probably
needs rebuilding and may have been overlooked.

From my Duo-Art experience, if you desire to get the utmost from the
expression for a Duo-Art system, remember that the accordion mechanical
settings as shown in the service manual are what I call the "static
settings".  To get desirable dynamic settings I used to construct a
graph of the ascending powers using the test roll and writing down the
pressure measurements taken with a vacuum gage and then readjust the
accordion mechanical settings accordingly to make the graph come out
linear.

The theme and accompaniment graphs should be plotted on the same piece
of graph paper so you can see that the theme for any given power is
always more than the same power for the accompaniment graph.

I used to do some tape recordings of before and after these adjustments
for a specific piano and what a difference it would make in the sound
of classical music.

Ellsworth Johnson
Spokane, Washington