Mechanics & adjustment
The carillon transmission is a series of wires and levers connecting key to clapper. Designs vary, but exaggeratedly, the mechanism works like a waterskier and boat: When the boat goes forward, the rope pulls taut and drags the skier along. If the boat goes backward, it just gives the rope more slack while the skier floats in place. On the carillon, depressing the key tightens up all the wires and linkages and pulls the clapper toward the bell. Pulling back up on the key will mostly slack the system as the clapper bounces away on its own. Some manual keys are even designed to work only one-way: the wire can be pulled down, but not be pushed up. This available slack is an important feature in allowing the bell to ring freely.
With a well-adjusted clapper, if the player pushes the key to the bottom, the clapper still hangs a few millimeters away from the bell. Enough momentum must be given given—that is, the player pushes hard enough—for the clapper to continue past this point to strike the bell. In this way, it is impossible to hold the clapper against the bell, disturb the vibration, and produce an ugly sound. The available slack in the system allows the clapper to travel this extra distance; if the wires and linkages were rigid, this escapement would not be possible (like a waterskier pulled with a pole instead of a rope). Once the key reaches the bottom, the clapper essentially detaches, or escapes, from the key, and flies freely toward the bell. A clean bounce and freely-ringing bell is guaranteed, since the player is not at all in control of the clapper—only gravity and friction act on it while escaped. This mechanism is analogous to the piano hammer escaping the jack to strike the string(s).
The left animation below demonstrates how the properly adjusted system works - turn on your speakers and click to play.
| Properly adjusted clapper | Clapper adjusted too tightly |
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The animation on the right demonstrates the way many players adjust, perhaps inadvertently, to make it easier to play softly or to have "better control." If these players always release the keys before the bottom, there is no problem with deadening the sound, since this allows clapper escapement anyway. All players push the keys fully down at least some of the time, though, because it allows better control of dynamics and timing the notes. Pushing the key fully down while the clapper is tightly adjusted will necessarily produce a deadened sound.
A perfectly designed and built instrument could be adjusted to allow an escaping clapper (like the left animation), AND it would be easy to play softly. Unfortunately, most carillons don't allow this, and the player must decide between the two ideals (see diagram below). I am investigating what in transmission design causes this, but have not yet found a good answer. I believe it involves friction in the transmission and return spring tension, since two notes identical in design can have very different adjusting thresholds. Because making ugly sounds is inevitable if the clapper does not escape, clappers should be adjusted so that it is impossible to hold them against the bells.
The piano
The piano uses a similar escapement transmission to the carillon's. While the piano is more complex, they are the same in that both instruments throw their strikers against the resonators. A pianist cannot possibly hold the hammer against the string(s), by design, because this would dampen the strings. The video below demonstrates a piano with the escapement mechanism disabled. This explains why pushing a piano key down very slowly produces no sound: not enough momentum is given to allow for the hammer's escape past the point of the bottom of the key. See the section on tone color for a discussion on controlling piano timbre.
A carillon must be adjusted to behave like a piano, where the clapper always escapes. If the weather did not affect the transmission, there would be every reason to permanently adjust it like a piano. Adjusting to allow the player to directly strike the bell, unmitigated by escapement, fundamentally changes the design and function of the transmission.
Keybed material
Compression of the keybed material is a factor in adjusting which complicates the situation. I've been referring to the bottom of the key, but this point is variable depending on how much the felt or rubber cushioning compresses. The perfect carillon would have a wood or other non-compressible key bed, but this would put too much impact on players' hands and wrists. The ideal then, is to adjust the clappers by compressing the key bed as far as it will be compressed while playing. This is difficult to judge, so I will continue to look into it.
continue to Tone color & bells⇾