Long ago, at the conservatory of the Hague, I used to have a yoga class directly before my harpsichord lessons. I now believe that this mad schedule was the working of some bad spirit who wanted me to spoil both: yoga, and harpsichord playing (he didn’t succeed). During yoga, I was as tense and rigid as the dried fish they sell here in Sweden at Christmas time. Well arriving at the harpsichord lesson, my body had gotten weak as pudding while my mind was all tense and jumpy in anticipation of the new and wonderful requirements of a Real Musical Education. “Technique, technique, technique!” my teacher chanted, the first time he jogged into the harpsichord studio, eagerly rubbing his hands.
No wonder that on one of those days, when I was touching up a few unisons, I tuned every note jerkily up and down again. My teacher’s eyebrows shot up in intelligent acknowledgement: “Aah, you always tune a little higher first – is that to make the string hold better afterwards? Very interesting method!” 28 years after this event I can disclose that I simply was very nervous. But there are methods that help harpsichords, clavichords or fortepianos keep their tuning and there are some things better to avoid when tuning. I am, naturally, talking about such instruments where the tuning pins hold well in themselves.
Four factors can work together to fool the tuner into prematurely abandoning a string that has not yet settled on its proper pitch. Tuning pin (lengthwise) torsion, tuning pin (sidewise) bending, and any overly enthusiastic turning up and down are all incompatible with the retarding effect of the friction at the bridge- and nut-pins. This friction delays, to varying degrees within one instrument (and in wildly contrasting patterns between instruments) the process of tension-equalization of the three sections of a string (the sounding section and the front and end sections). The string needs a little time to settle, time during which the pin should not be turned, twisted or bent.
There are two things to find out: 1) how much do the tuning pins twist before they actually move in the pin block? 2) how slowly do the strings react in a given instrument? On the intuitive understanding of these matters and on the getting-to-feel the moment when things move and settle, the tuner’s decision to turn, retry and leave alone will be based.
There are two things to avoid: 1) tuning too enthusiastically up and down. 2) bending the pin instead of turning. The first issue is most likely the result of a combination of an insecurity about hearing the pitch well, and of mechanical difficulties when turning the tuning hammer. Frequently, one’s inability to hear whether a note is slightly too high or too low is simply a matter of a slack concentration. Often it will be sufficient to let the only interesting question emerge clearly in one’s mind: is this note too high or too low? Make up your mind and correct according to your guess. If an ever so slight correction makes things worse, the guess was wrong, but then you have the right answer – the insecurity is cured and you can correct the pitch safely, fully focusing on the mechanical aspect of turning the tuning hammer. If you still should tune past the right pitch, it will not be much.
The second issue, bending, is either (if you use a T-shaped tuning hammer) a sloppiness that needs to be corrected: turn both sides of the hammer evenly and avoid pushing and bending sideways during that action. If you are using an inverted L shaped hammer (of the shape of a modern piano tuning hammer) sideways bending cannot be avoided. Why do these hammers bend the pin? Because the applied force is not, as in the T-model, applied at two points that lie at even opposite distances in line with the turning axle, but it is instead applied only on one side, far away from the turning axle. The force is hence transferred to the pin from one side only and the rigidity of the pin alone makes this principle work. A thin pin is less rigid than a thick one, and hence it will bend, albeit ever so slightly. These tuning hammers are, simply, worthless for being used on the thin tuning pins of most historical keyboard instruments.
Two actions of the tuner will help the string to settle into its final state: 1) play the note a few times while not tuning at all. 2) loosen your grip on the tuning hammer while checking for the last time, in order to make really sure you didn’t bend the pin by accident. For clavichords it will be necessary to touch at the dynamic level that will be most common when playing music. On fortepianos, some tuners have developed a habit of loud banging to get the string tension evened out. This is not good at all. One should indeed play the note fortissimo once or twice, that is: a musical fortissimo, not a grinding Beethoven-parody-sforzato. Otherwise several undesirable things will happen: 1) there will be too much wear on the nut pins, the hammer leather and the escapement hopper hinges (often strips of parchment that are difficult to replace). 2) the tension between the three string sections will in fact not even out, but instead be whacked out of balance by a too hard blow, and the tune-keeping afterwards will be less stable.
Only after this beginning, we will be able to talk cents, beats and deviations between temperaments. That is, if we also manage to keep the temperature and humidity in the room constant and if we avoid direct sunlight on the instrument.