Tone is crucial element of the piano’s sound, and its evenness and beauty is essential to the expression of music. If tuning is the adjustment of the strings’ tension to the correct harmonic pitch, the tone is the intensity and quality of the sound produced.
Although the basic character of a piano is modeled within its design, an experienced technician can modify a piano’s tone to the requirement of its owner by using a technique called voicing.
Any number of adjectives can be used to describe a piano’s tone. Metallic or wooden, harsh or soft, bright or mellow, all conjure up sound images. But whichever descriptions are used, the quality of tone is subjective. No rules prescribe how a piano should sound, other than that, its tone should be even throughout and, of course, be musical.
The instrument’s role should be considered. A grand capable of filling a theater or cutting through an orchestra may be altogether too much in a living room. As should the type of music to be played: a rich and warm tone may enhance a Beethoven sonata more than it would a modern jazz improvisation.
To this end, the piano should offer a tone that the pianist finds encouraging and pleasurable to play, as well as one that blends with the occasion. Much of the piano’s inherent tone derives from the design and construction of the strung back assembly. And this is the primary reason why all makes of piano sound different.
Certainly, during the first half of the twentieth century, piano makers took great pride in producing pianos with an individual tone character. The classic warm, mellow tone of a Bluthner stood in stark contrast to the powerful, metallic ring of a Steinway or indeed the rich, hollow sound of a Bechstein.
Even today, makers “engineer in” their own trademark sound through various design modifications. Stringing scales are calculated to require different degrees of tension. Soundboard dimensions are reworked to produce different response times. Various forms of sympathetic vibration are used to enhance the fullness of sound, including Steinway’s duplex scaling and Bluthner’s aliquot stringing.
These all contribute to a maker’s inherent tone character, which cannot be altered by voicing. Beyond this, however, there are number of factors that can be altered to enhance a piano’s tone. A room’s size and its content have an enormous effect on the way sound vibrations travel.
Hard and shiny surfaces reflect sound vibrations, particularly higher frequencies, resulting in brighter sound. Whereas, fabrics, carpet, and other soft furnishings absorb sound energy, creating a warmer, more rounded sound. So, by reorganizing a piano’s environment, it is possible to change its tone.
The shaping, positioning, and regulating of the hammer heads have significant effect on tone, as does the condition of the strings and bridges. As a piano ages, its original tone quality is gradually lost through use and deterioration, and an experienced technician can usually restore this.
Before any voicing procedures begin, the piano must be adjusted to its best condition. Since many uneven sounds perceived as voicing problems may actually be created by other faults within the action, keyboard, and strung back.
The piano must be accurately tuned to concert pitch, with its strings well seated on the bridges, and the action and keyboard are well regulated to ensure it produces an even, powerful, and accurate response.
This includes the reshaping of the hammer heads and subsequent realignment, so that they strike their strings squarely and simultaneously. Their smooth shape and striking action is essential for good tone. Only once this basic functions have been restored can a piano’s tone be accurately judged.
If it is then thought to be too loud, harsh, or brittle, it can be made mellower by softening the hammer felt. This is achieved by stabbing the felt with sharp needles in a very controlled and precise manner. If overdone or misdirected, the compression manufactured within the hammer head has the potential to collapse beyond repair and the dangers to the technician’s supporting hand are all too obvious.
If the tone is judge to be too mellow, then the hammer felt can be hardened by the application of hard-setting chemicals, such as cellulose. Before using these in the top treble, a technician must be sure that the weak tone is caused by the hammer felt being too soft and not by the striking position of the hammers.
Once the overall tone of the piano is perceived to be right, then the individual hammers are needled so that the tone blends from hammer to hammer over the entire compass. Only an experienced and trusted technician should be asked to voice a piano, for it is a job of great skill, concentration, and understanding.