The soundboard is the single largest piece of wood in your piano. It is the speaker of the piano. In order for the piano to have proper tone, the strings, bridge, and soundboard must be in tension together. To make this occur, the piano is designed and built so that the strings have a slight downward angle on both sides of the bridge. This angle is called downbearing. Along with this, the soundboard must have a slight upward curve which is called crown. The downbearing and crown must be maintained as precisely as possible. It takes very little change to dramatically compromise the tone and tuning of the instrument.

When the humidity drops, the soundboard shrinks and flattens, lowering the tension of the strings. The pitch will drop or become flat. The technician will have to perform a pitch raise to bring the piano back to the proper pitch before a fine tuning can be done. When the humidity rises, the soundboard absorbs moisture from the air, making it swell and increasing the crown. Now, the pitch will go up or become sharp.

The complex mechanical linkage that starts with the key that you press with your fingers, and ends with the hammer striking the strings is called the action. In almost all pianos, it quite literally has thousands of wooden parts that must all be precisely adjusted to work perfectly together. This adjustment process is called regulation. When the humidity changes, the precision is lost, resulting in the touch you have grown accustomed to changing and becoming inconsistent.

Just as doors and drawers become tight and difficult to move, the keys of your piano may respond slowly or even stick down in times of high humidity.

Likewise, just as doors and drawers become loose in dry air, the keys of your piano may rattle or become mechanically noisy. When the wooden action parts shrink from dryness, they become loose and can move around. This will lead to premature wear of these parts and costly repairs in the future.

Over time, constant changes in humidity and temperature levels, with the corresponding shrinking and swelling of the soundboard, will damage the integrity of the soundboard. This potential damage is most immediately visible in the form of pressure ridges and cracks in the board.

Piano strings are under tremendous tension, as much as 42 tons in many instruments. The strings are coiled around tuning pins that are driven into holes in a multilayered piece of wood, usually maple, called the pinblock. The individual tuning pin is actually slightly larger than the hole that it is driven into. The resulting tight fit is necessary for the piano to be tuneable.

When the humidity increases, swelling the wood, the tuning pins may become so tight that the technician has trouble making the delicate adjustments that are necessary in a fine tuning. When the humidity level drops, the pinblock will shrink, resulting in loose tuning pins. This can result in a piano that will not hold tune very long or even render it completely untuneable.

The strings of your piano are responsible for producing the musical sounds. With exposure to high humidity levels over long periods, strings become rusted and corroded.

At the junction where rusted strings wrap around rusted pins, rust corrosion forms a hardened bond between the two. Then, during a tuning, when your piano technician turns the pins to stretch the strings, the inflexible, rusted string snaps at this joint.

Please contact us for more information about this important aspect of properly maintaining your piano.