Harpsichord Monthly Plectrum & Jack Regulation Log

ContextA healthy Delrin plectrum has a clean, squared tip with a consistent bevel on the underside from prior voicing. Under a 5× loupe, look for micro-chips along the leading edge — they appear as irregular notches and produce a scratchy, inconsistent attack that voicing cannot correct. Quill plectra wear differently: the surface becomes fibrous and the tip begins to splay laterally, losing tonal focus and eventually catching on the string return. Flag any such jack in the log with "replace" before moving on — neither chipped Delrin nor splayed quill improves with further voicing.

ContextThe plectrum tip should extend past the jack face by approximately 0.5–0.6 mm for most 8' registers, and slightly less for 4' registers where string tension is lower. Use a dedicated plectrum gauge or the blade of a small caliper to measure any jack whose attack sounds thin, heavy, or inconsistent. Too much protrusion increases touch weight and accelerates string wear at the plucking point; too little produces a grazing contact rather than a clean pluck. Log the measured value and the direction of deviation for every outlier jack.

ContextThe plectrum should approach the string from slightly below, angled upward by roughly 5–10° from horizontal as it rises with the jack. This geometry ensures the plectrum snaps cleanly past the string on the upstroke and allows the tongue to pivot on the return without re-engaging. A plectrum sitting horizontally or tilted downward will tend to double-pluck on the return or produce an incomplete release. This angle is determined by the tongue's resting position — if it is consistently off on one jack, re-seat the tongue and verify that it rests correctly at the vertical stop.

ContextHold the jack body in your non-dominant hand and press the plectrum tip toward the tongue with a fingertip. A correctly voiced plectrum offers noticeable but not excessive resistance — calibrate your finger sense on a known-good jack first, then work outward from it. A plectrum that collapses with minimal pressure produces a thin, quiet tone and may fail to pluck cleanly in cold conditions. One that resists firmly produces a heavy, percussive attack and uneven key feel. Use a condition code in the log (e.g., S = soft, C = correct, F = firm) rather than relying on memory across a long session.

ContextHold the jack upright and nudge the tongue backward — the direction it travels during key release. It should move freely, spring back promptly, and stop at the upright position without leaning forward past vertical. Binding (the tongue resists or moves in jerks) typically indicates a humidity-swollen axle hole or a corroding axle pin. A tongue that falls forward past vertical places the plectrum angled too far below the string, producing a missed or weak pluck. Note the jack number and the precise symptom — this determines whether a re-seat or a full tongue replacement is the correct response.

ContextThe tongue spring — traditionally boar's hair, a thin steel bristle, or a synthetic filament — sits in a channel in the jack body and presses against the rear face of the tongue. Test by depressing the tongue fully and releasing it: a healthy spring returns the tongue sharply and decisively. A fatigued spring returns slowly or incompletely, causing the plectrum to remain partially rotated, leading to missed plucks on rapid re-presses or a dragging sensation on the return stroke. A displaced spring may allow the tongue to over-rotate backward past its normal range. Use a fine spring hook to reseat displaced springs; keep replacement spring material of the correct gauge in stock — it is inexpensive and prevents diagnostic confusion during sessions.

ContextWith each jack seated in its register slot, observe its vertical travel through the full key dip range. A healthy jack moves straight up and down without sideways wobble. Lateral play in the slot can cause the plectrum to miss its string or make contact with an adjacent string, producing a buzz or a double tone. Hairline cracks along the grain of the jack body are most visible under raking light held at a low angle — they appear as thin bright lines on the surface. A cracked jack body should be replaced rather than glued; wood cannot be reliably repaired at these stress concentrations and will split fully under normal playing tension.

ContextWhen a register is engaged, the jacks should shift laterally by approximately 1.5–2 mm — enough to align the plectrum directly over the string. Test by engaging the stop and playing in the low bass, middle octaves, and high treble in turn. A register that speaks cleanly in the treble but produces absent or thin tones in the bass often indicates that the register board has warped from uneven humidity exposure — common after an instrument moves through different climate zones. Even a 0.5 mm misalignment at the plucking point produces a significant change in tone quality or a complete non-response.

ContextRegister slide runners accumulate airborne dust and surface oxidation over time, creating friction that makes register changes feel gritty or heavy. Do not use oil or any petroleum-based lubricant — these attract grit and can migrate toward string-speaking areas and damper felts. The correct lubricant is pure paraffin wax: rub a small block of plain white candle wax directly along the runner surfaces and move the register back and forth several times to distribute it. A well-maintained register engages with a positive, light action and disengages smoothly without sticking. Stiffness that persists after waxing suggests the runners may need planing — a task for a qualified technician.

ContextThe damper rests on the string at key rest, stopping resonance between keystrokes. When the key is pressed, the jack rises and the damper should lift free of the string before the plectrum engages — otherwise the attack is muted and then brightens as the key travels deeper. Test by holding a note down for two full seconds and releasing it sharply — tone should stop within one vibration cycle. If it lingers noticeably, the damper is not seating. If the initial attack is muted and then clarifies, the damper is lifting too late. Causes include a bent damper wire, a compressed felt pad, or insufficient jack travel height to fully lift the damper before the plectrum engages.

ContextHold a flashlight at a low angle across the damper rail and examine every felt pad. Healthy felt is uniformly dense, slightly springy when pressed with a fingernail, and free of tunnels, pitting, or missing fiber patches. Moth damage characteristically begins on the underside of the felt and can be advanced before it is visible from above — when you remove jacks for other tasks, look at the bottom face of each damper. A compressed felt (flattened from years of seating force) can no longer stop string resonance fully; sympathetic vibration between adjacent strings becomes audible in bass passages and in quiet room conditions. Replace compromised felts — glued patches are a temporary stopgap only.

ContextThe buff stop mutes strings near the nut with small leather or felt tabs, producing a dry, pizzicato-like tone. When engaged, each tab should press firmly enough against the string to eliminate sustain but not so firmly as to prevent the plectrum from engaging. Play through the complete range with the buff engaged and listen for isolated bright notes within the otherwise muted texture — these identify tabs that have shrunk or stiffened away from their strings, a common finding with aged leather. Also confirm that the buff disengages fully: a tab remaining in partial contact when the stop is off will cause a persistently muted note that presents like a voicing problem and may take time to diagnose correctly.

ContextKey dip — the vertical travel distance from key rest to keybed contact — is typically 7 mm for the lower manual and 6 mm for the upper manual for historical-style instruments; single-manual instruments are often set to around 6 mm. Rest a small wooden dip block of known height on an adjacent key at rest, then use feeler gauges to measure the gap between the block and the surface of the fully depressed key at its front edge. Variation exceeding ±0.5 mm across the compass indicates that the key frame has shifted or that balance rail cloth punchings have compressed unevenly. Note outlier keys by position number rather than note name alone, since pitch standard and keyboard layout can change between sessions.

ContextDepress ten adjacent keys simultaneously, hold them for two seconds, then release all at once and observe. Every key should return to flush rest within the same short interval — no floating keys sitting fractionally depressed, no hesitation mid-travel. A key that rises slowly or stops short prevents the corresponding jack from fully resetting its tongue before the next keystroke, causing repetition failures. Causes include compressed balance rail punchings, a stiff tongue spring on the corresponding jack, an incorrectly positioned lead weight inside the key lever, or a front rail pin binding in its key bushing.

ContextA cipher is a note that continues sounding after the key is released — the plectrum is catching on the string return rather than escaping. A buzz from a specific key suggests a loose register fitting, a cracked jack body resonating, or a damper not fully seating. A muted note with normal key action points to plectrum under-protrusion, a collapsed tongue spring, or a jack seated in the wrong slot after previous maintenance. Playing at both pianissimo and fortissimo dynamics is essential: problems appearing only very softly (a plectrum barely engaging) are fundamentally different from those appearing only loud (a heavy plectrum forcing the tongue open). Mark every irregularity in the log by register, octave, and position number.

ContextMany regulation problems are register-specific. A jack may function correctly on the lower manual 8' while showing a stiff tongue on the 4' register because that register slot is fractionally tighter on that side of the board. Test at minimum: lower manual 8' solo, upper manual 8' solo if applicable, 4' solo, lute or buff stop if fitted, and full coupling with both manuals engaged. If the instrument has a 16' register or nasal stop, include those as well. Recording which specific register exhibits each problem cuts diagnostic time significantly, because it identifies immediately which register board, which side of the instrument, or which previous voicing session is responsible.

ContextVoicing reduces plectrum stiffness by thinning the material on its underside. Hold the jack in your non-dominant hand with the plectrum pointing away from you. Make a shallow cut on the underside of the plectrum — the surface facing away from the string when the jack is at rest — starting about 1 mm from the tip and sweeping toward it at a very shallow angle. Remove only 0.1–0.2 mm per pass and re-test each time. It is always possible to remove a second shaving; an over-voiced plectrum must be replaced entirely. Never work in poor lighting, and always direct the cutting stroke away from any fingers. A blade that tears rather than shaves cleanly needs sharpening before proceeding.

ContextDelrin plectrum blanks are inexpensive — typically $5–10 for a pack of 100 — and pre-cut blanks sized for most standard jack bodies are available from harpsichord supply houses. To replace: push the old plectrum out from below the tongue slot using a pin tool or thin dowel, insert the new blank until it seats flush against the tongue body, then trim to the correct protrusion with sharp scissors or a single clean blade cut. Voice the new plectrum to match surrounding jacks. For quill replacement, soak the raw quill strip in water for 20–30 minutes before cutting — dry quill splits along its grain during insertion into the tongue slot. Plan for a second voicing pass after 1–2 hours of settled playing, as new plectra shift slightly as they find their working position.

ContextA complete monthly entry should include: the date, the environmental readings from the pre-session step, a condition code for every jack in the instrument (not only problem jacks), and specific notes on any corrective action taken. Suggested codes: OK (no action), V (voiced), R (plectrum replaced), T (tongue adjusted or re-seated), S (spring replaced or re-seated), D (damper corrected), DEF (deferred to next session or technician). Using position numbers such as "Lower 8', position 23" rather than note names prevents confusion if the instrument is re-tuned to a different pitch standard or if the keyboard compass is extended beyond the standard 61 keys.

ContextThe comparative review is where monthly documentation earns its value beyond individual sessions. If position 14 on the upper 8' was voiced in April and requires voicing again in May, that two-month cycle is significantly faster than normal — investigate the plectrum material or the humidity history for that period. If damper felts in the bass are flagged across multiple consecutive months while treble dampers remain stable, this pattern frequently indicates a structural issue with the bass bridge or a cold air source positioned beneath the instrument on that side. Patterns of this kind are invisible without a sequential record to compare against.

ContextClose each log entry by writing any deferred tasks at the top of the following blank entry — not buried in current-session notes. Note any upcoming events that may affect regulation: a performance in a different venue or climate, planned transport, or a period of non-use exceeding three weeks. All three can alter damper felt compression and key return speed in ways that make the next session's findings atypical. Setting the calendar reminder before closing the instrument lid is a deliberate discipline: if you set it later, it may not get set at all, and the value of the monthly log depends entirely on the monthly actually happening.