I currently have a foot-pumped Armstrong Marque Ampico upright I'm
rebuilding.  The expression units are alone, and have no crescendos.
The piano has a vacuum gauge next to the Tempo indicator, and it tells
you how hard to pump as indicated on some of the older Ampico rolls.
That's how the expression is controlled.

If you were to add an ordinary suction box to it, you wouldn't get the
full Ampico expression, so in that way, it's probably inferior to an
Ampico upright.  It's also a single valve Amphion style stack with only
block [unit] valves, but no secondary valve chest.

If there's anyone else that has one of these, feel free to write to me,
because my rubber tubing had disintegrated, and I can't find many
diagrams for the foot pumped model.

Luke Lindblom