Hello Kurt, and MMD. Most Wurlitzer theatre organs which had
factory-installed pianos (and they were comparatively few) used
[dual-] pressure actions, designed originally by Robert Hope-Jones,
which played at moderate pressure from manual first-touch contacts,
and higher pressure from manual second-touch contacts, allowing a bit
of keyboard-controlled dynamics.
Many "organ pianos" had no keyboard as the pressure action with two
pneumatics per note took up much more room than a normal vacuum action
and spoolbox, as the pressure pneumatics were quite a bit larger than
they would be on a vacuum-operated action.
Bob Loesch
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