the turn of the screw

A while ago, a good friend asked me whether, in a Walter-style fortepiano action, one could reduce pre-touch by twisting the hammer capsle up one turn. It seems indeed that this is a simple action that would yield good results fast. One needs to look at a graph to appreciate the avalanche of problems a simple 180-degrees turn of the capsle will, in fact, unleash.


As one can see in this crudely jpg-ified version of my original vector graph of a Walter action, the amount of pre-touch is defined by the distance of the hammer beak (which is, of course, one part with the hammer shank a but gets here a separate letter f) and the escapement hopper (some call it a pawl). The brass capsle is the diagonal part at the left-hand side of letter b; it is screwed into the key end. By turning the whole assembly of hammer (a) and capsle (b) a whole twist counter-clockwise, the hammer beak would come closer to the pawl hook and that was the whole idea.

Think again.

The capsle is screwed into the key at an angle. Turning up means inevitably re-locating the hammer beak upwards but backwards as well (to the left, on this graph). The resulting greater overlap of beak and pawl means that the escapement occurs at a higher point. In practice, a whole outward twist of the capsle usually makes that the hammer escapes past the level of the string, or in other words, jams into the string before even thinking of escaping at all. How do we solve this?

Naturally by trying to reduce said overlap. This can be done by slightly bending the capsle shaft towards the player (on the graph: to the right). But what happens when we bend the shaft to the right? Because the capsle, as said before, is mounted at an angle, it will not only move away from the pawl and towards the player, but also upwards. In other words, re-adjusting the escapement in the described manner will very likely reduce the (already reduced, see above) pre-touch to beyond zero: the hammer beak will not even slip under the pawl any more. At the end one would either have to reverse the whole action and live with the original pre-touch, or cut layers off the beak leather in its present position, in the hope of making the action work again. On can also despair and call a tech – better late than never. And I have not even mentioned the – at the end of all this – necessary administrations for regaining the proper function of the hammer check (e).

A fortepiano tech would have a few tricks to work around many of these problems: she/he would, for example, after turning the capsle only half a turn, have the equipment (and experience) to completely re-shape the shaft angle for an optimal function in the new situation. But this work is extremely time consuming, and most of the time really not necessary at all. She/he would also be verbally equipped as to convince the pianist that slight deviations in pre-touch (we’re talking here about a range between, perhaps, 0.8mm and 1.5mm) are not nearly as crucial for a regular touch-sensation as a properly set-up escapement and a properly working hammer check. I began at that end and have tried to convince my friend to stay away from the capsles of his piano. (Ah. Hum. I am sure that he would have been able to solve the matter most brilliantly, of course!)

Think, for another example, that you want to reduce the length of the plectra of a whole register in your harpsichord. Of course there is a screw or a wedge at the end of the rack that can easily be turned or readjusted for bringing all the jacks of a register closer to the string. Many people will also have thought of the necessity of reducing the string-overlap of the plectra after this. But here the real problems begin: many plastic jacks have tiny screws on top that help to regulate the overlap. Turn them clockwise and the overlap gets less. But wait! The angle of the plectrum also changes. Turning all the jack screws in a whole rank’o’jacks inward in order to regulate the plectrum-string-overlap will expose all sorts of secondary irregularities you never knew about – half of the jacks will all of a sudden seem too long, since their plectra won’t return properly. Also the entire pluck-sequence between the register you’re presently working on and the other registers will be upset. So, in a way, one can be happy if there are no adjustment screws on top of the jacks, although one will have to cut all the plectra shorter by hand. In any case one will probably have to re-locate the dampers, because they will, in most cases, have come too close to the opposite string.

What I want to show here is that most harpsichord or fortepiano regulations that involve changes of distances, the turning of screws, cutting away material or adding shims of paper are likely to trigger some chain reaction. In average harpsichords or fortepianos there are far too many screw heads exposed and accessible for real comfort. I would guess that around a third of the work of a professional harpsi-tech involves the undoing of other’s regulation mistakes, as opposed to true maintenance. It is true, most of the screws can serve to get a regulation better. True too, many people have a very technical mindset and, although no professionals, are perfectly able to understand the relatively simple mechanics of these instruments.

But most of the time the human mind wants it otherwise. “Do this get that” it shouts, simultaneously holding up flashing big ugly signs with the word “because” written on them. Make the jacks shorter and improve the touch. Make the jacks longer and improve the touch. Reverse staggering and you’ll be surprised. Fine-tune the coupling mechanism because the builder couldn’t do it. Take the leads out of the key fronts and put them into the back, it always works. Make the keys lighter and you’ll play more crisply. Change strings and get a better sound. Make the soundboard even thinner and the instrument will get louder. Make the jack rail more flexible and you’ll be playing with more dynamics (I am not kidding, I’ve heard that one). Eat fish and you get smart.


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