Voicing and Piano Hammer Maintenance
Have you noticed that your piano sounds harsh, bright, excessively loud, or tonally inconsistent across different ranges of the keyboard? Despite routine tunings, perhaps you recall it sounding more pleasant or “warmer” years ago. If so, your piano may benefit from a standard maintenance practice called voicing (also called tone voicing or tone regulating).
Voicing is a broad term encompassing a variety of procedures where hammer felt is manipulated in order to improve the piano’s timbre, dynamic range, and tonal evenness.
The amount of voicing a piano may benefit from varies, and the degree of refinement possible depends on the piano’s overall design and condition.
What Is a Piano Hammer?
Modern pianos have 88 hammers (one for each note). Piano hammers are constructed of a wooden core called the hammer molding, with compressed layers of wool hammer felt attached around the molding. The result is a pear-like shape, with a small, rounded surface at the top of the hammer, termed the strike point.
The job of a hammer is to efficiently transfer energy from a piano key to the respective note’s piano strings, and to generate pleasing tonal qualities from the instrument in the process. The rounded nature and small surface area of the strike point are important ingredients for the effectiveness of this operation. Similar to how hitting a drum with different mallets produces different sounds from the same drum, the shape, size, and rigidity of the material on piano hammers can have a profound effect on the tone, sustain, and volume the piano produces.
Hammers and Their Wear Process
As the piano is played, each hammer’s strike point wears as it repeatedly contacts the strings, creating string grooves in the hammer felt. Some degree of string grooves is normal, but over time, string grooves can become so deep that the piano’s tone becomes compromised and uneven from note-to-note. The longer and deeper a hammer’s string grooves, the larger and flatter the hammer’s strike point becomes, compromising the hammer’s shape and negatively affecting the piano’s tone and dynamic range. As this gradual process occurs, the piano’s tone is often described as “loud,” “bright,” “less focused,” or “thuddy.”
Correcting the hammers’ shape and “voice” through various voicing procedures described below will make the sound of the instrument more pleasant and even again. If your piano’s hammers are left unserviced, the tone will continue to deteriorate, and your hammers may require replacement sooner than if these services had been performed when suggested.
Voicing services are grouped into two categories:
Fine Voicing
The process of manipulating existing wool fibers in the piano hammers with needles or other tools in order to produce a more even and palatable tone from the piano. The degree and recommended frequency of fine voicing maintenance can vary significantly depending on piano use-type, frequency of use, and condition.
Hammer Filing (also called hammer reshaping)
In cases of considerable hammer wear, it may be necessary for the technician to file or “reshape” the hammer felt before fine voicing can be performed. Unlike fine voicing adjustments which manipulate existing wool fibers, hammer filing is the process of removing worn top layers of hammer felt, exposing a fresh layer of felt from underneath. Hammer filing is usually meant to restore a smaller strike point for flexibility in subsequent fine voicing.
In cases where hammers show extreme wear, with a flat strike point and deep, long string grooves, the technician may instead recommend replacement of the hammers.