Technical Library

ACTION I: How the harpsichord works

Entire Contents Copyright © 2010 CBH
Next 1K gifBlank 1K gif

Harpsichord jack 22K jpegIntroducing the harpsichord jack…
Almost everyone recognizes the distinctive sound from the pluck of the harpsichord, but exactly how this is accomplished is a mystery to many: I could never fathom how the harpsichord worked until I was able to see one close up. With many of the written descriptions either ridiculously simplistic, or plainly inaccurate, I trust this clear explanation may help your understanding.

Integral to the plucking action of the harpsichord (or virginal, or spinet…) is the jack. There must be at least one jack for each note—larger harpsichords with several choirs of strings will have more. In the traditional instrument, the jack is made from a slip of wood, often smooth fruitwood like pear, or beech. The jack body must be long enough to reach from where it rests on cloth at the back of the key, to up between the strings. All the jacks are held in alignment by the guide or register. This allows the appropriate jacks to rise when their key is played, and then return freely by gravity when the key is released.

It is the quill (or plectrum) which actually contacts and plucks the string. Regularly cut from the spine of the primary flight feathers of birds, ravens were particularly prized for this purpose. Today, modern plastics like delrin or celcon are more commonly used, and last longer. The quill is inserted into a mortise punched through a separate small piece of wood called the tongue, allowing the quill to project almost perpendicularly—or a few degrees above perpendicular—from the face of the jack. Because the quill mortise extends almost to the edges of the tongue, a wood with an interlocking grain like holly must be used to prevent the mortise breaking out the sides of the tongue. Each tongue is pivoted in the top of the jack on a concealed axlepin and sprung by a spring. Boar bristle was commonly used for the springs, but also leaf brass or wire depending on the tradition. The entry hole for the spring is just visible in the photo below the tongue. It is the job of the spring to always bring the tongue to its vertical rest position. The bottom face of the tongue is beveled to suit the corresponding cutout in the jack body, and often a tiny silencing pad of thin leather is glued to the jack at that point to prevent excess noise.

It is the special arrangement of the tongue which enables the quill to pluck the string when the jack rises, but offer no resistance when the quill attempts to return below the string as the player lifts his finger from the key. Without this design, two plucks would be heard each time a note is played—the first when intended, and an unintentional one when the note is released. The jack returns by gravity, the bottom of the quill lightly brushing the string as the tongue swings a little backwards, allowing the quill to escape below the string. The spring returns the tongue to its vertical position, and the quill rests just below the string, ready to pluck again in an instant. The cloth damper, wedged in a slot (damper slot) cut in the top of the jack itself, silences the vibrations of the string at this time. The upper limit of travel of the jack is fixed by the padded jackrail, without which the jacks could bounce out of the instrument with vigorous playing.

Many harpsichord makers have shown their ingenuity in jack design and materials, some more successfully than others. Today, the highest quality instruments use jacks firmly based on historic models to allow the best function and feel, even though modern materials might be substituted for some parts. For a discussion of various jack models used by makers around the world, you can refer to our page on Wolfgang’s Jacks. The jack used for our photograph was one of those collected by Wolfgang Zuckermann in the late 1960s, and made by Joe Marshall, an American expat in Bangkok. His jack was one of the most historic in design.

Movie thumb 2K jpeg Movie 1K gif Wolfgang’s Jacks
The jacks collected by Wolfgang Zuckermann from makers around the world for his 1969 book The Modern Harpsichord.
YouTube logo 2K gif

Action index:

CBH Icon 1K gif Technical Library overview
CBH Icon 1K gif Harpsichords Australia Home Page