Underneath the manual keys and the foot pedals there are felt dampers. These reduce noise while the organ is being played. Over the years this felt gets compressed and hardens. When this happens you can hear knocks and taps as the organ is played. The noise is often worse from the pedals as these often have a strong return spring that can thump the pedals back up to the resting position.
It is a relatively straight forward operation to replace the felts and eliminate noise during playing. Any sideways movement will also be removed during this process to ensure quiet operation.
Above you can see how much dirt builds up under the keys. The green felt discs are hard and worn out. Below they have been replaced, and the dirt and debris removed.
The centre pin felts are also replaced, and the pins are greased. Next the front bat pins are adjusted to remove sideways movement.
The old brown pedal felt has been replaced with new red. The pins have been greased and the pedals are cleaned and replaced.
You can find almost anything underneath a pedal board!!