Hi,  While I do not profess it to be absolutely silent, I do make
a quiet suction unit for pianos and organs.  It is capable of extreme
suction, but I have it designed that way on purpose so that it can be
run very slowly.

The box is 8" x 8" x 9" and includes a speed control to be mounted
inside the organ or piano case.  It is also available with a second
speed control which can be made available to the owner.  On a restored
reed organ, the unit need only be run at a minimum speed to achieve
operating vacuum levels.  On a well restored player piano, the box may
need to run a little bit faster, but is still well within an acceptable
noise level.

I have found it to be quieter than boxes that are available from the
supply companies.  Please contact me if anyone is interested or has
other questions.

Sincerely,

Allen Moe