Piano Quality Control & Assurance 4 — Questions and Answers
Question 1: A QC technician finds that several treble notes have too much sustain even with the damper pedal not engaged. What is the most likely cause?
- Dampers in the high treble are missing — this range is intentionally undamped by design (Correct answer)
- Broken damper springs in those notes
- Sustain pedal rod is bent
- Hammer felt is too soft
Correct answer: Dampers in the high treble are missing — this range is intentionally undamped by design
By design, grand pianos typically have no dampers above approximately F6 because strings in the high treble are short enough to decay naturally.
Question 2: Which measurement tool is used to check the consistency of key dip during regulation QC?
- Dip block (key dip gauge) (Correct answer)
- Feeler gauge
- Digital calipers only
- Tuning lever
Correct answer: Dip block (key dip gauge)
A dip block is a small block of precise thickness placed beside the key to measure whether the key descends the correct distance.
Question 3: A piano string breaks shortly after the instrument leaves the factory. Which QC failure is most directly implicated?
- Incorrect string gauge or improper tension relative to speaking length and pitch specification (Correct answer)
- Improper hammer voicing
- Excessive key dip
- Incorrect bridge pin spacing
Correct answer: Incorrect string gauge or improper tension relative to speaking length and pitch specification
String breakage is most often caused by over-tensioning relative to the string's gauge and speaking length, a manufacturing or stringing error.
Question 4: What does 'down-bearing' on a piano bridge refer to?
- The downward pressure exerted by strings on the bridge, transferring vibration to the soundboard (Correct answer)
- The weight of the cast iron plate pressing on the frame
- Pedal rod pressure on the trap work
- Force applied by the tuning pin on the pin block
Correct answer: The downward pressure exerted by strings on the bridge, transferring vibration to the soundboard
Down-bearing is the angle-created downward force of strings pressing on the bridge, which is critical for efficient soundboard coupling.
Question 5: During factory QC, what does a 'playing-in' or 'run-in' procedure accomplish for a new piano action?
- Wears in the felt and leather contacts to reduce initial stiffness and even out touch feel (Correct answer)
- Sets final regulation dimensions
- Tunes all strings to pitch
- Voices hammers to target tone
Correct answer: Wears in the felt and leather contacts to reduce initial stiffness and even out touch feel
Playing in a new action compresses and conditions the felt and cloth parts, stabilizing touch weight and reducing initial friction.
Question 6: In piano manufacturing quality control, what is the purpose of a 'string break angle' inspection at the bridge?
- Ensuring the string changes direction properly over the bridge pin to maintain down-bearing (Correct answer)
- Verifying string color coding for gauge identification
- Checking string alignment to hammers
- Measuring speaking length
Correct answer: Ensuring the string changes direction properly over the bridge pin to maintain down-bearing
The string break angle over the bridge pin determines how much down-bearing is generated, which must fall within spec for proper tone production.
Question 7: A QC auditor finds that the sostenuto pedal on a grand piano catches dampers it should not affect. The most likely cause is:
- Sostenuto rod is positioned too high, contacting damper tabs that were not depressed when the pedal was activated (Correct answer)
- Sustain pedal spring is too weak
- Damper felts are too thick
- Pedal lyre is misaligned
Correct answer: Sostenuto rod is positioned too high, contacting damper tabs that were not depressed when the pedal was activated
If the sostenuto rod is set too high, it will engage tabs of dampers that were never lifted by keys, causing unintended note sustain.
Piano Quality Control & Assurance 4
A QC technician finds that several treble notes have too much sustain even with the damper pedal not engaged.
What is the most likely cause?