Jeff - I love it "in the weeds", so ask about whatever interests you. It doesn't take any longer to tune the harpsichord than it does to tune a piano. However, it does have to be done more often. Once a month is usually what is necessary as opposed to the normal twice a year tuning for a piano. Most people who own a harpsichord learn to tune it themselves, which has become possible with the advent of low cost electronic tuners.
As you stated, there are many factors that contribute to the tone. The fact that the strings are plucked rather than struck in a piano, is one factor. The wire is another. The wire we use nowadays is low-tension brass and steel. This wire is produced for the harpsichord trade and attempts to duplicate the type of wire used when these instruments were first built. The braking point of this wire is quite a bit lower than in modern piano wire, but the harpsichord may have a cumulative tension of up to 5,000 lbs. whereas a piano can be 10 times greater. As a result, the high tension piano wire is not needed and, in fact, tends to lessen the tone quality when used in a harpsichord.
The soundboard also plays a major role in the tone of the instrument. What it's made of - how thick it is - how much (or little) tapering of its thickness in certain areas - etc. all have a huge effect on the quality of the tone. To a lesser extent, the case itself is a contributor in that there is no cast iron plate in a harpsichord to withstand the tension of the strings (it's not needed in a relatively low tension instrument). The plate tends to eliminate the case from the tonal landscape. In a harpsichord, the case resonates as well, so its material, thickness, and method of construction plays a role in the overall tone.
Lastly, the pluck point plays a tremendous role in the tone. Let's assume a given string is 48" long. Where along its length will that string be plucked? Do you pluck it 5" from an end or right in the middle at 24"? The closer it's plucked to either end of the string, the more nasal the tone will be. As the pluck point approaches the middle of the string, the sound becomes much richer and more mellow. Most harpsichords use a pluck point of about 1/10th of the string length (less in the upper ranges of the instrument). Of course, the pluck point is decided by the builder and, once built, it cannot be changed. There are obvious limitations. In a harpsichord, you couldn't have a pluck point anywhere near approaching the middle of the strings, as the length of the keys would be impossibly long. On some old, virginal style instruments like the muselar, a mid-string pluck point is possible because the strings run from left to right instead of front to back. This allows for normal length keys while still employing a mid-string pluck point. As with so many other things, there is a price to be payed with a mid-point plucking point. It tends to make the strings vibrate so wildly that the dampers have a hard time dampening the strings when the player's fingers are removed from the keys.
Sorry for the long winded answer, but sometimes the weeds are thick.:rotflm:
Ernie