[pianopianos article "understanding the tonal characteristics of the piano"]

To analyse the tonal characteristics of a piano is to judge the following:

• Attack (the immediacy of the tone)*
• Clarity/Pronunciation/Definition
• Depth
• Frequency Balance: proud in high / mid / low frequencies†
• Sustain: how long the note/tone sounds
  
  * it is possible that this can be related to preparation/maintenance of the hammers, rather than the actual instrument.
  † the piano's actual frequency response, not the brilliance of the initiation of the note, as that is directly related to the voicing of the hammers, rather than the instruments resonant characteristics.

The tone of a piano is dependent on 3 main factors:

• Quality of Design and Build
• Quality of Materials
• Quality of Preparation and Maintenance

Quality of Design and Build

(Note: We have highlighted the main components for you)

Both design and build go hand in hand, as without the instrument being designed and built to a high standard, high quality materials are wasted and expert preparation can only have little gain. The design of the piano will include the precise calculation of the scaling on the frame which will determine the length, position and tension (and best suited gauge) of the strings to achieve the desired pitch and evenness of pronunciation and sustain. The scaling of the strings must be optimum for clear and defined pronunciation of each note. A poor frame design will give the piano little chance of ever sounding good, as the frame is the single most important component of the piano. The frame must also ensure that it can withstand up to 20 tonnes of string tension! Being the backbone of the piano, if the frame (cast iron) is not fabricated with accuracy, the tone between identical models of piano can vary hugely. Imperfections in the frame are certainly not wanted!

The frame design will also determine the contour of the soundboard (which is fitted underneath the frame) and the position of the bridge, which transmits the string resonance to the soundboard. The soundboard is the large resonating diaphragm that amplifies the string resonance - very much like the cone of a speaker. The contour of the soundboard, its thickness, edge and central crown (dome-like shape) will determine its frequency range, sustain and projection.The design of the bridge, such as its position, the choice/composition of material and its shape will be primarily responsible for how efficiently the string resonance is transmitted to the soundboard. The soundboard is braced by ribs, to provide strength and stability of the soundboard for the lifetime of the piano. The quantity and positioning of the ribs will have an effect on both the longevity and resonance of the soundboard. Consistency in the design of the soundboard, its bridge and ribs, is most important in achieving a consistent tonal character between models. This is the most organic part of the piano and therefore prone to variance in end quality. It is not just the design and build, but indeed the specification in the selection of timbers.

The design of the cabinet/case and backposts/beams to provide additional strength, will also effect the tone and sustain of the piano, relative to the density and rigidity of this acoustic framework. Some pianos feature tone collectors (bolts) which run from the frame through the soundboard directly into the backposts/beams, typically concentrating on the centre of the frame, to further increase rigidity. The more rigid and dense the acoustic framework is, the more resonance is concentrated within the soundboard.

The wrest plank (tuning pin block) is a dense hardwood block/plank, usually multi-laminated (modern pianos), which is drilled to hold the tuning pins. The design, composition and crafting of the wrest plank is indeed one of the most important of 2 factors in the piano's ability to hold its tune. The tuning pins are set/held in the wrest plank and are rotated to adjust the tension of the strings to achieve the correct pitch. Without being at correct pitch, the piano is simply playing the wrong notes! Without good tuning stability, the piano is frequently out of tune and when out of tune, pianos sound awful - therefore quality of tone is inaudible!

The action and keyboard of the piano are the mechanical components, which translate the movement of your fingers to the hammers striking the strings (this is how the piano falls within the percussion family). There are approximately 1,320 parts composing this section of the piano. The length and angle of each moving part will effect the amount of leverage in the touch. The weight of each part will effect the overall weight, resistance and, in fact, the speed and repetition. Absolute precision in the design, engineering and build of the action is crucial in the end product serving reliably and efficiently with good response and control. An inefficient action and keyboard will compromise the ability for the piano to have a broad dynamic range and be played with speed. The dampers rest with pressure on the strings to prevent them from resonating, and are individually lifted from the strings when depressing a key to allow that note to play. The sustain pedal will lift all dampers at once, when depressed. The dampers need to be both of adequate length and the felt of suitable cut, to successfully dampen the string(s) without much of an audible harmonic. The weight (grand) or spring (upright) must apply adequate pressure to apply the damper to the string(s), without there being too much resistance when depressing the keys. Although the keyboard and action are primarily mechanical components, they do in fact play the role in both 'initiating' and 'terminating' the tone altogether.

Quality of Materials

In vice versa to the above, poor materials can ruin the efforts of good design and build quality.

The frame on very older pianos was initially made of wood, which suffered greatly from fluctuations in humidity and therefore tuning was far from stable. Of the few pianos still in existence with a wooden frame, it is most likely to be warped and ruined by the frequent infestation of woodworm. Thankfully, the better pianos since around 1900 featured an iron frame, which immediately proved to be infinitely more stable!

The quality of the piano wire (steel) and copper-wound bass strings contributes to the purity of the note, sustain and stability.

Solid straight-grained spruce is the best timber for the soundboard due to its optimum balance of weight to strength: light enough to resonate freely, strong enough to withstand the down bearing from the strings. Cheaper pianos often have laminated spruce soundboards which, although strong (cross grained), have less ability to resonate. Spruce selected for higher density in grain (annual rings), with uniformity, is superior producing a broader tone range and extended sustain. If the specification is very strict with little tolerance, provided the design and crafting of the soundboard is precise, then this typically variable part of the instrument will produce a consistent tone from model to model.

The bridge is usually made of the most hard and dense wood, such as maple, as its purpose is to transmit resonance from the strings efficiently and quickly to the soundboard. The better pianos usually have a vertically laminated bridge, as the resonance travels more quickly and directly through the laminations. If vertically laminated, the bridge will be capped. For this rock maple is prime, and boxwood is a treat - usually used in the treble register.

The ribs are usually spruce and these need to work as though they are part of the soundboard, to resonate with the soundboard, not against it.

The hammer heads are usually a dense hardwood like maple or mahogany. Different woods can have different weight, and therefore affect the performance and weight of the touch. The hammers are covered with a high tension felt to provide an even and firm, yet delicate, surface to strike the strings.

Quality of Initial Preparation and Ongoing Maintenance

The quality of design, build and materials is almost impossible to appreciate if the piano has not been prepared or maintained properly.

The Preparation of a new piano is the checking and adjustment where required of the regulation of the action, keyboard, dampers, hammers and pedals to ensure that all moving parts are correctly set and aligned. Each key must feel and respond identically, although there is usually a very gradual difference across the range from bottom A to top C, as the hammers are of different size and therefore different weight respectively.

The principle factors in preparation are:

hammers must be aligned correctly so that they are evenly spaced and have even coverage of the string(s);

the distance the hammer is from the string(s) prior to depressing the keys;

when the 'jack' pulls away from the hammer butt/roller to allow the hammer to continue towards the strings on its own momentum;

catches the hammer on its return from striking the string(s) and holds it to allow the jack to reposition under the hammer butt/roller when the key is returned, for quick repetition;

should start to lift/pull the dampers from the string(s) when the hammer is half way towards the string(s);

key height and touch depth are checked and leveled if required. Key bushings are checked and eased as necessary to ensure free playing without sticking or stiff key movement;

must be adjusted correctly so that all notes are affected equally as required, such as the sustain pedal lifting all dampers from all strings simultaneously;

the piano will need fine tuning, as the art of voicing cannot be performed accurately without perfect tuning. Fine tuning is to adjust the tension of the strings to achieve the correct pitch (A440hz) with the bi chords (2 strings per note) and tri chords (3 strings per note) in perfect unison, avoiding 'phasing' or 'beating' which produce tonal impurities and unwanted harmonics;

the intonation of the hammers to adjust the hardness of the hammer felts which in turn can dramatically change the amount of brilliance in tone. The piano can be adjusted to produce a mellow, neutral or bright tone, to any degree and in various levels across the range. Also, 2 identical pianos regulated identically will seem to feel different if the hammers are voiced differently. Although you cannot actually feel the hammers striking the strings, harder hammers will sound brighter and therefore produce more tone with less effort than hammers that have been voiced mellow. Therefore, the brighter instrument will seem to have lighter and more responsive touch, but the touch is in fact identical.

Ongoing maintenance is beyond just regular tuning, with small adjustments to the regulation of the action as the piano wears, voicing of the hammers as they compress with use - eventually requiring reshaping/facing to file away the string impressions (grooves) restoring the 'tear-drop' shape and an even surface. The felt bushings in the keys, where the pivot pin on the balance rail and the aligning pin on the front rail enter the keys vertically, will eventually wear, causing excess lateral movement in the keys and therefore these felt bushings will need to be replaced. Small, yet frequent adjustments to service your piano properly will keep the instrument in top order. If you play a fine instrument, yet it has been neglected, its performance will not be true to its real abilities. This must not alarm you to be concerned of high costs, as the servicing of a piano is exceptionally inexpensive relative to that of motor cars or appliances, yet a quality new piano has quite possibly a hundred years of use to be enjoyed. Properly maintaining your piano is protecting your investment.

see [pianopianos article - "Yamaha Pianos"]