the jacks

The first crucial element in my unusual action design, is the jack.  I have iterated through a number of radical designs already, all on paper, as I have gradually refined my ideas about this instrument, over about the past 5 years.  The points of commonality are that the design must be uncommonly cheap and easy to fabricate, *without* the well-equipped specialty woodshop (which is a non-negotiable pre-requisite for building almost any other serious musical instrument).  And, it must accommodate a sustain (damper-lift) pedal.

I sure have taken a lot of flack (well, good-natured skepticism, at least) from the ancient-instruments community, for my insistence on the sustain pedal!  But this is exemplary of how my philosophy and aims differ critically, from those of the majority of builders today, who are only concerned with making increasingly accurate copies of historical instruments.  I am glad for those builders and their painstaking research and efforts.  As well as making good instruments in their own right, they have contributed massively to the knowledge in the field, and although I do not hold myself constrained by the boundaries and practices of the past, I have liberally borrowed from the knowledge and ideas that I have found there, through the help of the aforementioned historically-accurate builders.  Lack of knowledge of (or respect for) the past seems to be the main flaw which led to the dead-end of the "revival" harpsichords of the early 20th century.  The return to historical designs was a welcome relief from those awful, piano-inspired revival instruments, but unfortunately, the lesson learned seems to have been "don't try anything new, it's bound to fail".  Even if this is the statistically-likely outcome, I still see value in persisting to try to find those rare and valuable new things which actually improve the instrument in a lasting way.  Of course, this view presumes that the instrument is not already perfect, and that there may be new sounds and new purposes for it in the future, which go beyond anything heard in the past, *without* destroying or debasing the underlying nature and beautiful tone of the instrument.

So yes.  We must have a sustain pedal.  This, in turn, means that the normal operation of the harpsichord jack, must be changed somewhat.  Normally, as the jack comes back down after plucking the string, the plectrum touches the string a second time.  It's not as hard a touch as the first time: instead of plucking the string, the spring on the tongue allows the plectrum to be pushed aside by the string as it falls past.  And right after (or even simultaneous with) this second touch, the damper mutes the string.  So, normally, the second-touch is no problem.  If it's audible at all, it's not objectionable, it just adds to that "harpsichord sound", a slight bit of noise upon damping.  However, if there's a sustain pedal, then the dampers are no longer directly attached to the same jack as the plectrum.  If the pedal is pressed down, then the string is not damped when the key is released, so noise from the second touch becomes more prominent.  Also, the second touch is likely to at least partially disrupt the vibrations of the string, set in motion at the first touch (the pluck).

(Many small lautenwerk harpsichords skirt past these problems, although having no dampers, because the undamped sustain time of the strings is so short that they might as well have dampers: the second touch doesn't disturb the vibrating string, because it's hardly vibrating any more anyway.)

In order to prevent second-touch, I attach a guide-wire to the tongue.  As the jack returns, the guide-wire encounters a blade-like sloped surface which causes it to pull the tongue back, just enough that the plectrum misses the string.  The guide-wires and the associated battens which hold the blades, are located in the space above the jacks.  Thus, there is no conventional jack-rail above the jacks; their upward motion will be stopped by other means, down below.

I built a prototype jack, to test some of these ideas.  My design has already changed, I will not build any more like this, but still the photos are probably helpful in describing the basic operation.

I used a bent piece of sheet aluminum for the tongue, instead of wood.  A nail (point clipped off) passes through horizontally, to form the axle.  The "plectrum" is the end of a nylon wire-tie (in actuality, I will probably have to use "real" plectrum material, i.e., the plastic called Delrin, because nylon wears out and bends and changes shape too much).  A hole is drilled at an angle, through the sloped front face of the wooden slip, and coming out the back.  A doubled-over piece of thin nylon monofilament passes through this hole, to form the spring.  It's visible, faintly, to the left of the plectrum in the photo above.  The two ends of the monofilament come out the back and are taped down with duck tape.

Up to this point, despite the unusual construction (considerably easier for me to fabricate than the traditional wooden jack), it still *behaves* just like a regular jack.  The spring is soft enough that the weight of the wooden slip is easily enough to make the tongue swivel and the plectrum return past the string, in the usual way: no hanging-jack problem seems likely.  Yet, in the upward direction, the angled plectrum catches the string and forces the tongue firmly forward to its stopping point, independent of the smaller force from the spring.  So I guessed right on the geometry.  This jack would work in a regular, horizontal harpsichord with no sustain pedal, just fine (except for lacking a damper).

But in the following photos, you can see that I've added the guide-wire to the top.  It is superglued into the corner of the tongue, on the other side from where the monofilament return-spring rides.

The guide-wire has an L-shaped bend with a horizontal segment at the top, folded over double at the end to keep the sharp end of the wire out of the contact area.  This horizontal stub is what encounters the 45-degree sloped blade.  On the way up, the sloped blade pushes the guide-wire forward towards the string, causing it to flex because the tongue is already against its forward stopping point.  On the way down, the other side of the blade pulls the guide-wire back, causing the tongue to swivel backwards on its axle, and thus pulling the plectrum back just enough to miss the string.

This is an exaggerated degree of bending, in situ it will just be a few degrees, enough to pull the plectrum back perhaps 2 mm or so.

As I mentioned, however, my design has changed since this one.  In order to fit all the jacks and dampers needed into the available space (the width of the gap between the wrestplank and the soundboard, about 2 inches, necessarily limited because the highest and therefore shortest strings are just barely longer than this), I need to make the jacks even narrower.  Also, the metal tongue is not desirable, because it doesn't give the right kind of seating for the plectrum (for this prototype, I just superglued it in there).

So in my next design, yet to be prototyped, the jack body will be square-section basswood, 1/8"x1/8".  A diagonal cut will separate the body from the tongue, which is just a continuation of the same wood.  A wire, firmly fixed to the side of the jack body, will go straight up along the side of the tongue, turn 90 degrees and pass through a hole in the tongue (this section of wire comprising the axle), then 90 degrees and back down; one end of the same wire will loop back up and form a backstop for the motion of the tongue, by standing in front of the lower, beveled portion which comes forward as the main part swings backward.

There will be a nylon spring, as in the prototype above, but the tongue will need to have an angled slot cut in its lower, beveled face, to accommodate the spring.

The upper end of the tongue piece will be drilled, front-to-back for the plectrum (I may use a specially-shaped hand-tool as a mortice-cutter to make these holes rectangular, after drilling the round pilot holes), and with a hole in the top for the guide-wire.

Thus, this jack will be like the "middle third" of a conventional jack: if you shaved off both sides until the whole thing was no wider than the tongue, and then added a wire to replace the axle whose fixed end supports you just shaved away.

(The bottom ends of my jacks will widen out into about the same width as a normal jack, to allow them to pass through rectangular guide-slots which will keep the rotational error to a minimum; the wider bottoms will also add weight, which will help them return when used in a horizontal context; the clavicytherium will of course have to address the issue of returning the jacks, more explicitly.  However, the wide dimension of the jacks, in the horizontal context, will go across the width of the keylever, so that the jacks still pack closely together on each keylever, separated only by their narrow dimensions; as opposed to normal jacks, where the long dimensions line up along the length of the keylever.)

An example of the useful knowledge I've gained from examining the methods of the past, is that I can make my own "drills" for drilling these small-diameter holes, by sharpening thin nails and pieces of steel music wire, or by using clipped-head pins and needles, depending on the diameter.  Initially I tried to use tiny storebought "hobby" drills, in an adapter in my drill press, to make holes like this; but it's entirely unnecessary to use spiral-cut drills *in wood* at such small diameters, and it only makes the drills frustratingly fragile and flexible.  A handheld electric drill, or even completely-manual means such as a bow-drill or crank-handle, are quite sufficient, given the right special purpose jigs to guide the drill direction.  (Very different terrain from drilling fiberglass PC boards, my other main area of experience with small drill bits.)