I did a work related to voicing at my piano workshop yesterday.
Voicing means what adjusting piano's tone or volume.
We use needles or sandpapers when we do voicing.
When we stick needles to piano's hammer felt the tone color is changed to be soft.
And when we file piano's hammer using sandpapers the tone color is changed to be clear.
Finally I could finish the work with no problem.
★埼玉県三郷市のピアノ工房