The first step is to set the height of the keyboard.

As I explained before wood dimensions change with variation in relative humidity; more specifically, it changes across the grain (tangential) whereas along the grain (longitudinal) it is stable.

When the humidity falls below 50% rel. the case starts shrinking: its depth decreases, its length stays the same. Since the soundboard is glued near the top of the case it will move towards the bottom (on which the keyboards rest) and with it the strings. The jacks will also shrink (they become thinner and narrower) but their length will not alter. At one point the strings will be so low that the dampers in the jacks don´t touch them anymore (harpsichord doesn´t damp). If humidity decreases further the plectrum will not return under the string after being played (harpsichord doesn´t repeat).

To compensate for the shrinkage of the case you can lower the position of the keyboard by turning the hexagonal screws located under the bottom of the instrument anti-clockwise (out of the instrument) usually equal turns left and right. To find their right position, turn on all the registers (don´t forget the 4´) and feel, by touching the front of the keys lightly, if there is a play of about 2 mm. This play is the travel of the key from rest position till the first plectrum touches the string. If the play is not equal in bass and treble you can adjust it by giving one of the hexagonal screws more or less turns than the other.

In case the humidity goes above 50% you have to start raising the keyboard to compensate for the expansion of the case.

The second step is to engage and disengage the register levers.

You should feel a good amount of friction (needed to keep the register slide in its on or off position). If the lever is difficult to move, loosen the lever screw a bit. If you feel little friction, tighten the screw.

If you feel an accurate on and off position and the slides don´t move during playing, the lever screw is good.

Perhaps you made a picture of the jacks and strings when you received your instrument; such a picture shows by how much the plectra surpass the string. It helps to put the register slides back in their original position (if not, you can always make one when you are finished with the maintenance and are satisfied with the result).

Take the jack rail from the instrument (note that it is not symmetrical left to right: in Flemish and French instruments the bass side is hollowed out more, in Italian instruments there can be papers added under the felt to adjust the key dip).

Turn one register on and see how far the plectra protrude the strings. A rule of thumb is that the plectra protrude a bit more than the thickness of the string they pluck (which means that in the bass they protrude more than in the treble). If it is more (over-plucking) the instrument will be louder (but also will play heavier) with the limit that it doesn´t repeat well. If it is less (under-plucking) the instrument will be softer (and play lighter) with the limit that some (or many) plectra don´t reach the string.

You can change the position by turning the brass capstan screw to which the plectrum points on the register slide. For over-plucking turn the screw anti clockwise (out of the register slide) for under-plucking, clockwise (into the register slide) till you reach the desired result.

Now turn this register off. The plectra should just not touch the strings. If the off displacement is not big enough some plectra will (very lightly) keep plucking their strings. If it is too big the back of the jacks will start touching the neighbor strings, making those strings sound strange. By adjusting the capstan screw facing the back side of the jack you will get a good ¨off¨ position.

Follow this procedure for all registers.

The fourth step is to turn one register on, play all the notes and judge wether you like the way it plucks (the way it feels) and the way it sounds. Some notes will be too loud or too soft (see ¨voicing¨) and you will have to take a knife and a voicing block to change them. If the entire register sounds too loud (and feels too stiff) your register slide is still not in good position (repeat step 3).

Once you are satisfied with the result repeat this step for all the registers.

My voicing aim in double manual harpsichords:

1. ‣both 8´ registers more or less the same volume. The upper manual 8´ (front 8´) is, because of its timbre, more present than the lower manual 8´ because of which it can be voiced a bit softer (this gives also a mechanical advantage because of the smaller leverage of the upper 8´ key)
   

2. ‣the 4´ will act often as a color for which it can be voiced softer than the 8´ (the higher pitch of this register makes it very clear anyway). It is a matter of taste.
   

3. ‣4´ plucks first followed with a little staggering by the back 8´ (lower manual 8´) and last the
   

4. front 8´.
   

My voicing aim in single manual harpsichords:

1. ‣both 8´ registers equally loud (in case of 2 x 8´)
   

2. ‣the 4´ about as loud as the 8´ (it could be used as a solo register)
   

3. ‣back 8´ (register nearest to the soundboard) plucks first, front 8´ last (or 4´ first, 8´ last). This in contrast to what I wrote earlier. I think that this configuration (back first- front last) has a mechanical advantage because of the bigger movement of the back 8´ jack compared to the front.
   

The fifth step is to turn all registers on and play the keys individually.

There should be a little delay between the individual plucks (staggering). If the staggering is too big it could be that the last plucking 8´ register is too loud compared with the first plucking (the stiffer a plectrum the more it lifts the string and the deeper the key goes before plucking). If it is too small, probably the first plucking register is too loud.