Here we see the pallets being re-covered. In a tracker action organ, the pallets are operated directly by wooden links (called trackers) connected to the keys. Where this is not possible due to the distance from the console (keyboards) a pneumatic motor can be used to open the pallet. An electric solenoid cuts off the admission of high-pressure air into the motor which collapses to pull down the pallet. The connection to the console is by electricity, and these days is computerised so that there is only one wire between the two.
While this may seem convoluted, experience has shown that it is the most reliable way to connect the keys to the pipes if the direct mechanical action is not possible.