Getting motors to run quietly inside a piano case can be very difficult.
Any slight noise will be transmitted to the sound board and will be
amplified if the motor noise is not isolated right at the motor.

The four sources of noise are motor hum, motor rumble from imbalance,
bearing noise and noise from motor movement caused by improper
mounting.  The original installations were very good in most respects
and should be duplicated whenever possible.  Sometimes something as
simple as a leather strap can make the difference between a quiet and
a horribly noisy piano.  Duo-Arts are especially difficult.  Try to
copy the original setup exactly.  Even the center of gravity and mass
of a motor can cause problems if not the same as the original.

For an upright Duo-Art, the motor should be .25 hp., however a modern
motor is probably more efficient and could be smaller.  The starting
torque is low, so don't worry about capacitor start, etc.  Unfortun-
ately most modern motors are horribly noisy unless they are very
expensive.  They rumble and the bearings are noisy.  If the only
problem is the bearings, they can be replaced with precision bearings,
but this will be expensive and they might not work if the motor depends
on bearing slop for its functioning.

I would look for an old motor and repair it if necessary.  The best
would be a piano motor, of course.  I have used industrial quality
motors that were purchased surplus.  My favorites are D.C. motors.

They can be connected to a Variac [variable transformer] (or electronic
voltage regulator) and a rectifier and can be speed-matched to the
installation.  Good D.C.  motors are very quiet except for a little
brush noise, and this noise does not travel very far.  Brushless D.C.
motors are generally not speed controllable unless they have the
correct controller and should only be used by someone who understands
them completely.

The best solution is an external pump.

Spencer Chase