French harpsichords usually employ the first approach, undercutting the undersides of the playing portions of the keys quite a bit to eliminate as much forward weight as practical. This approach can be used on other instruments as well. Since my keyboard is made of basswood, instead of a hardwood like beech or chestnut more typical of the Italian harpsichord-making tradition, I elected to balance my keys by weighting, which I think may also give them the slightly heavier feel of hardwood key levers.
By balancing my keys individually on a thin slip of wood, I found all of them to be front-heavy: not surprising, given that these keys are on the short side as a result of the Trasuntino's significantly angled gap and smallish wrestplank depth. I elected to use two sizes of weights: one 6 mm wide and 4 mm long, the other 1/4" wide and about 7/16" long, the latter cut by hand from a lead wire several feet long.
First I drilled holes 9/32" in diameter for the large weights, as far back as I could without getting too close to the rack pin:
This took care of the coarse balancing and made the keys back-heavy.
To complete the balancing, I placed a U.S. penny (weight 2.500 g) at the front edge of each sharp and centred on the scribe lines of each natural. This added weight at the front and tipped each key forward again. I then put a small weight on the key and started shifting it backward very slowly until the key just tipped back, as shown below:
I marked the final position of the small weight and drilled a hole for it. A few keys needed more than one small weight, but in the end all were balanced.
Balancing with a temporary weight in front gives a little extra reliability to the return of the keys when released, which will be assisted further by the weight of two jacks resting on their far ends. Some say that this method of balancing also reduces the possibility of an accidental brush of a key triggering an unwanted note, since the keys will require deliberate pressure to respond.
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