I would like to indicate that the Accompaniment boost was not used with
the "Soft" operation of the Duo-Art piano.    This boost function is only
used when playing 88-note rolls or when the DANCE lever is turned on.
When the Duo-Art switch is set to OFF (88-note), then the accompaniment
boost feature is turned ON so that the vacuum level is raised to around
10" to 12" of vacuum.  Without this, the 88-note rolls will not play
properly.

The 88-note accompaniment boost was achieved by two different ways in
the various pianos:

1. A separate pneumatic that is mechanically linked to the
Accompaniment regulator.  This is more commonly called the "88-note
pneumatic".  A screw allows for adjusting the desired vacuum level.

2. 1 or 2 of the accompaniment accordions are turned ON so that more
vacuum is applied to the stack.

Some pianos have a DANCE mode which operates the #8 (1248)
accompaniment accordion pneumatic.  This also boosts the vacuum.

As far as I know, this is the only use for boosting the volume of the
Duo-Art player.  Trying to boost the vacuum levels in the player to
compensate for the opening of the SOFT hole in the tracker bar was
never used to my knowledge.

Pete Knobloch
Tempe, AZ