Voicing
Pianos have their own personalities. The original design establishes it’s basic character. The tone or quality of sound is adjustable. Voicing is the process of modifying a piano’s tone.
Factors of tone can be hammer hardness or softness. Hammers wear, so instead of an egg shaped point contacting the string they may have become flattened and blunt. Hammers need to be filed to restore proper shape. The action becomes out of adjustment so that touch is uneven and the ability to play softly and lightly lessens.
Usually what I find is that as the hammers are used the tips become harder and the tone become bright and harsh. And it becomes uneven from note to note.
Simple voicing can be a short session of needling the hammers. This can be done a little with each tuning to maintain nice tone.
If the piano is very bright a longer session is needed to do proper shoulder and tip needling.
Other Factors to Consider When Voicing a Piano
Placement of the Piano
Room acoustics and a hard floor do reflect high frequencies. Hard rooms with no padded furniture, rugs, or drapes can make it very hard on the ears. I have been in some where the echo made it hard to tune.
Brighten Tone
Sometimes tone needs to be brightened and a hammer hardener such as thinned lacquer is applied. Often in the top sections. Although if too much felt is left on the hammer from the factory the tone can be brightened just from a proper filing and removing excess felt.
Wear Over Time
Sometimes working with the hammers is not enough. There may be other issues effecting tone such as worn parts. Loose hammer flange pinning, loose hammer heads, hammers not aligned with the strings, action out of regulation. On old pianos bass strings can become dull and thuddy.
Overly Bright Tone
Often Asian instruments get a bad reputation as being too bright. They come from the factory that way and neither the store or the technician have taken the time to improve the tone. People live with their pianos for years not knowing that the hammers can be voiced to a much more pleasant, richer, and warmer sound.