The jack: the heart of the mechanism
As the centerpiece of the transmission between the musician’s finger and the string, the jack is a marvel of handcrafted precision. Far more than a simple piece of wood or composite material, it is the guardian of your harpsichord’s voice. To understand how it works is to understand the high standards required for the maintenance of your instrument.
As a harpsichord maker and piano tuner & technician, I carry out major restoration work and complex maintenance directly at my workshop located in Montpon-Ménestérol 24700. For on-site services, I regularly intervene within a local radius around Montpon.
To optimize travel costs, I also organize scheduled group service tours in my three key sectors: around Pau and Oloron (Béarn 64), as well as around Bellême (Orne 61) and Le Mans (Sarthe 72).
Anatomy and functioning of the jack :
Each key of the keyboard activates a jack vertically. Its mission is twofold: to pluck the string as it rises and to pivot out of the way as it descends to avoid striking the string again.
The body : the vertical structure that supports the entire assembly.
The beak (plectrum) : the point of contact that "plucks" the string.
The tongue : the pivoting part that allows the beak to pass the string silently on the return.
The damper : the small piece of felt that stops the string's vibration as soon as the key is released.
The adjustment screw: the link between the finger and the string
Under each jack is an adjustment screw (or pilot) that plays a fundamental role in playing precision. This height adjustment is the pivot for an essential parameter : the "gras" (the gap).
This term refers to the space between the plectrum at rest and the string. This interval is crucial because it determines the depth of touch required to trigger the sound. Using this screw, the distance is adjusted to achieve a perfectly consistent trigger. It is within this spacing that the sensation of control lies: a well-regulated mechanism is one that is felt, then forgotten.
Did you know? Historically, makers adjusted each jack by adding or removing small shims of paper or leather at its base. While the screw offers undeniable convenience today, the precision required remains the same as that of the old masters.
The tongue and its spring : precision mechanics
The tongue is the pivoting part that carries the beak. Its proper functioning relies on the adjustment of its spring (often made of boar bristle or brass):
- Resistance during plucking : the spring must be firm enough to hold the tongue securely in place at the moment the plectrum plucks the string.
- Repetition : conversely, after passing the string, the spring must instantly return the tongue to its resting position. A weakened spring makes this return inconsistent, thus preventing the rapid repetition of the note.
The art of voicing: why a poorly cut beak changes everything
The sound of a harpsichord depends not only on the quality of its strings, but on the exact geometry of each beak. Neglected voicing transforms the instrument:
A beak that is too long or poorly cut makes the touch feel hard or "brittle," and can cause parasitic noises.
Poor equalization creates a sonic imbalance between notes, making musical performance frustrating.
As a maker, my work consists of sculpting each beak with a scalpel to achieve uniform resistance under the finger and optimal tonal clarity across the entire range of the keyboard.
Materials and durability: making the right choices
Wood vs. plastic
Today, two main families of jacks exist, but their behavior over time differs radically:
The wooden jack (my technical choice) : this is the traditional standard. Wood is easier to maintain over the long term. If it shifts or warps slightly, it can simply be precision-planed to regain its perfect fluidity within the register guide.
The plastic jack : although introduced as a modern solution, plastic ages poorly and becomes brittle. Its lack of standardization makes adaptations complex, and it cannot be reworked once it has deformed.
Delrin or bird quil ?
The choice of plectrum material influences the life of your instrument.
Delrin : this high-performance polymer offers exceptional stability. It is unaffected by humidity variations and requires no lubrication. It is the ideal solution for a reliable instrument that is always ready to play.
Natural quill : although historical, quill is organic. It wears out faster and becomes brittle if it is not regularly oiled.
The damper : the master of silence
The damper must brush the string just enough to silence it instantly without slowing the jack's movement. Imprecise adjustment or an unsuitable material (causing a "click") will undermine the characteristic clarity of polyphonic lines.
Maintenance and diagnostics: the sensory balance
It is often through subtle sensations that the instrument signals a need for attention :
- Touch : unusual resistance or a feeling of weakness indicates that the balance of the "becquetage" (plucking resistance) is shifting.
- Sound and silence : a loss of clarity, a note that no longer responds during rapid play (spring), or a lingering resonance (damper) are symptoms of a need for adjustment.
Regular maintenance by a "facteur" is not limited to repairing a breakdown; it is a work of precision that preserves the integrity of the action, ensuring that your instrument remains a source of pleasure, rather than a constraint.