Voicing is the process of removing inconsistencies of tone, attack and decay. The most desirous sounds of a piano is when all the notes maintain an even voice. Each note is neither louder, softer, harsher or duller than it’s neighbour. To achieve this universality a piano technician must spend time with the piano in regulation. Regulation is the attuning of all the mechanical parts in the piano to the manufacturers specifications. Pianos are made mostly of wood, and wood has a tendency to alter in shape slightly especially in response to large swings in humidity, but also merely with the passing of time and use. The piano technician must adjust these mechanical parts to ensure the piano maintains it’s optimal playability. Evenness in key height, key depth as well as hammer checking all contribute to evenness of sound and touch.
Once the regulation has been taken care of, the more specific art of hammer manipulation is possible. Piano’s with a lot of use tend to sound very bright and even brash or harsh. This is caused mostly by the packing of the hammer felt. The hammer is constantly mashed against steel strings which eventually leave deep grooves in the felt of the hammer. Hammers are made of compressed felt. This compressed felt is made at a consistency that creates a desirous piano tone. Neither too soft, nor too loud. After prolonged use the hammer felt is further compressed where it strikes the strings creating the above mentioned grooves and a harsh or brash sound, being beyond the specifications of the piano hammer manufacturer. A piano technician has the ability to card the hammer with sandpaper to eliminate the grooves and thereby ridding the piano of it’s brash sound and restoring the hammer to it’s original consistency. A hammer may be able to withstand 4 or 5 hammer reshapings. The carding of a hammer may prolong the life of the hammer and will definitely improve the tone of the piano. Once the hammer has been carded, further manipulating of the hammer may be needed to restore the piano’s original tone. During the reshaping of the piano hammer, the technician will often stick needles (4 or 5 sewing type needles encased in a special tool) into the shoulders of the hammer to lengthen the decay of the notes. Once this has been accomplished certain notes that stand out from the others will be further needled to match their neighbours. On rare circumstances, if the tone of the piano after reshaping of the hammers is too dull, a small amount of lacquer may be applied to the hammer to bring out a brighter sound.