I have produced the control system for several pipe organs using electro-magnetic solenoids for the stop actions. I just finished a new one where we use pneumatic cylinders to provide force. A pneumatic system can actually work without producing much noise if set up correctly. So we are very happy with this new organ in St. Johannes church, Stavanger, Norway.
We use 58 pneumatic angular cylinders controlled over a CAN bus from the console draw-stops, supplemented by a combination action control computer (running Linux/Busybox).
The images show some of the pneumatic cylinders for the stop action within the organ and for pedalboard/keyboard coupling mechanics within the console.
Hey I just wanted to let you know,