John Grant asks about Recordo documentation [210517 MMD].
I am not sure what is contained in John Tuttle's compendium.

 [ See https://www.player-care.com/system88.html and
 [ https://www.player-care.com/recordo-which-one.html and
 [ https://www.mmdigest.com/Archives/KWIC/R/recordo.html 
 [ -- Robbie

Recordo does not have an 'Expression ON/OFF' switch because the
expression holes are outside the 88-note playing range. However,
when 88-note rolls are played, the expression is at 'minimum'.
So generally there is a control knob of some kind to raise the
vacuum level(s) when playing 88-note rolls.

My Autopiano/Standard player has a indexing lever to set and retain
a selected vacuum level without having to constantly hold the lever
in a set position.

The original Recordo system used a choker kind of vacuum setting box.
There is photo posted by John Tuttle in the MMD Archives and has been
commented on. That photo is of the original 10-level system. That
same box is described in Bob Billings' paper.

In Art Reblitz's book is shown the arrangement of the modified system
which had 5 levels of vacuum. This is a leaker system which allows air
to bleed into the vacuum system and so moderate the pump pressure.

The Recordo system used a split hammer rail to produce a different
playing intensity between Bass and Treble. There was a system developed
around 1926 which used the 4 ports to produce a 16-level vacuum
control; these rolls were made with an 'A' prefix to the roll number.

This third variant used a control box which probably used vacuum
control of playing intensity difference between Bass and Treble. This
type therefore has a split pneumatic action stack. I seem to remember
that Wurlitzer may have used this control box but I can't be sure.

I think it is important to establish what Recordo version is in the
piano. There are two initial questions:

1. Is the stack split?
2. Is the control box a leaker type or a choker type?

Do you have a picture of the control box?

Paul Rumpf
Melbourne, Australia