Piano Quality Control & Assurance 3 — Questions and Answers
Question 1: A piano's repetition spring (in a grand action) is too weak. What symptom will the player experience?
- Slow repetition — the hammer fails to reset quickly after a note (Correct answer)
- Keys that feel too heavy
- Excessive hammer bounce on loud notes
- Dampers that rise too slowly
Correct answer: Slow repetition — the hammer fails to reset quickly after a note
A weak repetition spring fails to hold the repetition lever in position, causing sluggish note repetition at fast tempos.
Question 2: What does 'hammer line' (or 'line of hammers') inspection verify in a grand piano QC process?
- All hammer striking points are equidistant from the strings at rest (Correct answer)
- All hammers weigh the same
- Hammer felt density is uniform
- Hammer shanks are the same length
Correct answer: All hammer striking points are equidistant from the strings at rest
Hammer line inspection ensures every hammer travels the same distance to the string, producing even tone across the keyboard.
Question 3: In factory QC for upright pianos, which test specifically checks for buzzes and sympathetic vibrations?
- Chromatic scale played at forte while technician listens and touches cabinet panels (Correct answer)
- Measurement of key dip with a dip block
- Tuning pin torque test
- Soundboard deflection test
Correct answer: Chromatic scale played at forte while technician listens and touches cabinet panels
Playing loudly while touching cabinet parts isolates which panel or component is resonating and causing unwanted buzzes.
Question 4: A piano exhibits 'double striking' — the hammer hits the string twice unintentionally. Which regulation point addresses this?
- Back check distance (Correct answer)
- Let-off distance
- Key dip
- Damper timing
Correct answer: Back check distance
The back check catches the hammer after it rebounds; if set too far, the hammer can bounce back and restrike the string.
Question 5: During a soundboard inspection, a technician measures crown using a straightedge. What does adequate crown indicate?
- The soundboard retains its upward arch, maintaining downbearing pressure on the bridge (Correct answer)
- The soundboard has been properly lacquered
- Ribs are evenly spaced
- The bridge is centered
Correct answer: The soundboard retains its upward arch, maintaining downbearing pressure on the bridge
Soundboard crown creates downbearing force on the strings via the bridge, which is essential for transferring string vibration efficiently.
Question 6: When performing key weight (touch weight) QC, what are technicians typically measuring?
- The grams of force required to depress a key at a specified slow speed (Correct answer)
- Key return spring tension
- Hammer mass in grams
- Balance rail pin friction
Correct answer: The grams of force required to depress a key at a specified slow speed
Touch weight (down-weight) is measured in grams and should be consistent across the keyboard, typically 50–55 g for grand pianos.
Question 7: What is the primary goal of 'seasoning' a piano soundboard before installation?
- Stabilizing moisture content to prevent future warping or cracking (Correct answer)
- Hardening the wood fibers for brighter tone
- Applying varnish to seal the grain
- Pre-stressing the ribs for optimal crown
Correct answer: Stabilizing moisture content to prevent future warping or cracking
Seasoning brings the soundboard's moisture content to the equilibrium level of the intended climate, preventing post-installation dimensional change.
Piano Quality Control & Assurance 3
A piano's repetition spring (in a grand action) is too weak.
What symptom will the player experience?