Dampers

Dampers are installed after the preliminary voicing, as it is easier to see the quills without them.

Dampers come in the form of a strip of felt about 1 cm wide and several feet long. A portion is pushed into the damper kerf of the jack and cut off from the back, leaving the damper a bit long. To determine the correct length, the damper is trimmed from the front while the register is in the off position (i.e. further from the string). If the damper sits on the string in this position, it will also work in the on position (closer to the string).

It's important that the dampers not be excessively long in the off position; otherwise, when the register is turned on, the damper may reach past its own string and damp a neighbouring one. This also means the register's off position cannot have the plectra too far away from the strings, otherwise by the time the register reaches the on position, the dampers may be too close to a neighbouring string.

I'm using so-called flag dampers, which are more or less square in shape and flat along the bottom edge. These dampers allow the jacks to hang slightly from the strings, which makes transposing the keyboard easy. If the jacks actually sat on the keys, the resulting weight and friction might interfere with transposition.

The bottom edge of these dampers should be just slightly above the tip of the plectrum. This little bit of slack keeps the action reliable during changes of humidity.