The small 'bumper' pneumatics in an Ampico even-out the supply under
quiet playing, and are there to overcome particular aspects of that
systems' regulator.  The Ampico [regulator], in common with other
bass-treble systems, has negative feedback built-in so that its suction
level is little affected by the amount of incoming air.

The Duo-Art, being a Theme-Accompaniment system, has no fixed point
to base its feedback on (the stack is sometimes Theme, sometimes
Accompaniment) so instead embraces the regulator's suction "droop" as
more air is admitted.  The droop is a feature of the expression system,
and is what causes large chords to drop out on an 88-note roll when the
suction is set very low.  Adding an Ampico-style small reservoir won't
have any impact on this underlying behaviour.

However, we know what droop a Duo-Art is expected to have from its test
roll: it's what the "play / don't-play" tests are investigating.  On
the #3 test roll we have the following figures for Accompaniment:

Level 0: 1 note plays, 8 notes miss (really, more than 1 should miss)
Level 1: 3 notes play, 5 notes miss
Level 2: 4 notes play, 8 notes miss
Level 4: 7 notes play, 14 notes miss

You can see therefore that the miss point (a level -1 if you were) is
just below level 0, 2 notes below level 1, 4 notes below level 2 and
7 notes below level 4.  In other words, the expected droop at very low
levels is just over one duo-Art level per 2 playing notes, with droop
decreasing as the levels rise.  Duo-Art rolls are coded for this.

So, you can expect some droop when playing an 88-note roll on a
Duo-Art.  It's meant to happen!  If, say, it's set to level 4, it
should always play chords of 7 notes and start to drop out before
14 notes.  If it'll only play smaller chords it's probable that the
system is leaking -- either a static leak or one associated with the
playing of notes -- and hence swamping the regulator.  Adding
reservoirs doesn't stop the leaks!

Julian Dyer