More debugging

I've been working on and off with the Trasuntino for the past two months, trying to get a handle on the troublesome repetition in the tenor and bass regions. What stymies me is that the jacks work perfectly well in the upper two-thirds of the instrument, yet they become troublesome about an octave below middle c'. No harpsichord will repeat perfectly right down to the bottom of the keyboard, but my problem areas are much too high up for me to feel completely comfortable playing the instrument.

After soliciting suggestions from the harpsichord list, I learned something very interesting that pertains to my difficulties. In a nutshell, the longer a string is, the thicker it must be in order to maintain a reasonable amplitude of vibration. "Reasonable" in this case means an amplitude that is not difficult to damp out when the jack comes back down. If the amplitude can't be controlled, repetition will be compromised.

The list experts reviewed my stringing schedule and a consensus developed that the schedule was too light in the lower regions by at least one, if not two, gauges. Several suggestions were offered that advised me to end with gauge #1 in the lowest regions (0.020"). One maker said that anything less than this would behave like a "loose clothesline". Since heavier wire must be under greater tension to reach the correct pitch, the resulting increase in stiffness means the wire won't flap around as much when vibrating.

Part of my stringing problems stemmed from a slight misunderstanding of mine regarding how stringing by numeric progression works. The original instruments on which this was practiced had keyboards extending up to d''', and starting higher by those extra two notes would allow heavier gauges to be used by the time one reached E in the bass. The Trasuntino only goes up to c''', which means I finished with gauge #3. I should have started with 9 strings of #9, and not 10, in order to get the correct results.

The new schedule has the crossover points between gauges occurring on higher notes than the current schedule. In adjusting the stringing to conform to the new schedule, there will be minor changes in the alto and treble, while the lower part of the instrument will require extensive restringing.

The changes higher up are so minor that I decided not to bother with them: besides, this isn't the problem area. So I applied the new schedule only from c' downwards. Because the crossovers occur higher up in this region, I was able to recycle a lot of existing wire by removing strings and tuning pins together, shortening each string slightly, and reinstalling it about a fourth higher. By reusing wire, I saved myself the trouble of depleting my wire supply, and also gained the advantage of using wire that has already stretched out over many months and developed its tone.

From F# downwards, new wire in gauges #2 and #1 was required. Since the numeric progression rule dictates that 2 wires of #2 and 1 of #1 are called for, there wouldn't be enough to reach C unless I wanted to use even thicker gauges , and excessively thick wire has its own problems (it can sound dull or otherwise strange). So I bent the rule by using 3 of #2 and 4 of #1. The short-octave note GG/BB was left unaltered, as it was originally strung quite heavily (.022" red brass).

I tried this schedule out on the front 8' at the beginning of October, and found that the stiffer wire did indeed improve repetition noticeably, without completely curing the problem. I decided to give the new wire several weeks to settle down and develop its tone.

Now, at the end of October, I've concluded the new wire sounds good, so I'll keep the changed schedule. Recently I've been revoicing the plectra in the restrung region, as they are not so well matched to the new wire. My sense of the register as a whole is that my initial voicing back in August was too heavy, so I went ahead and thinned all the quills in the entire register. With a lighter touch, the repetition has improved even more, to the point that I think the problem is almost cured. Next, I'll do the same to the back 8'.

Amplitude and string vibration have a more crucial effect on the playability of a harpsichord than I initially suspected. Originally I thought that, provided the scale was correct for the intended pitch level, one could string a harpsichord with purely sonic considerations in mind, but I now see that the mechanical reliability of the action is impacted by the string schedule too.