The piano is extremely sensitive to climatic changes. In a sense the piano is a living thing. This because much of the construction of a fine piano is of wood. Woods remain hygroscopic long after they are not “living” or after being made into something beautiful like furniture or a piano.
In my hundred plus year old home I have noticed that every fall our interior stairs begin to creak and a crevasse opens in the fall at my living room ceiling above the crown molding. This seasonal change occurs like clockwork. There are many other examples we can all think of to be sure. None of which are surprising at all if we understand the nature of wood. Quite simply, wood expands with moisture or humidity and contracts with dryness. There are scientific reasons forthis. Understanding the effects of atmospheric changes around your pianois easy.
The piano soundboard is the largest single component of the instrument. The purpose of the board is to transduce sound to the environment surrounding the piano or to the air. Piano sound is a combined phenomena involving the structure itself, felted hammers, steel and copper strings, wood bridges and soundboard. A complex “action” delivers hammers to steel and copper wrapped strings which then in response vibrate. The vibrations are carried to the soundboard by hardwood bridges. The soundboard is arched and loaded with pressure from the strings and responds to energy in the form of vibrations. The purpose of the soundboard is not really to amplify sound but to receive vibratory pulses generated by the various parts of the sound generating systems of the piano and convert them into air movement.
When everything is right for a piano we say it is stable. In order for a piano to remain stable it must be in a controlled environment that is conducive to the woods, felts and other natural materials which are parts of it’s make up.
With moisture- all of the woods expand. Many felt parts do as well. The soundboard in particular becomes larger and broadens in scope. With this, pitch goes up as strings are stretched tighter across the bridges which are connected. The cabinet parts also expand, as do keys and countless other parts. Everything gets larger and pitch goes up. Friction also increases as parts which are calibrated to work with minimal necessary friction now must fight additional resistance to movement and increased weight. Common conditions include sticking or slow keys, slower action response, higher pitch and less defined tone.
With dryness other negative conditions prevail, some with damaging effects to the piano. When a soundboard gives off moisture it becomes smaller as if shrinking. When the soundboard gives off so much moisture that it sinks below a reasonable normal level, it will crack. This is a common condition in pianos. Without a near perfectly controlled environment cracks are almost a certainty. Clicks may develop in the action and tuning pin torque will be compromised. Piano tuning will not be stable. Some would say the tuning will not “hold”. Even the lacquer or varnished finishes of the piano may crack.
It is very interesting that tone quality and tone color also change with higher or lower readings in relative humidity. Piano hammers absorb moisture form the air and produce less brilliant tone. They are heavier and less focused because of moisture and expansion within the hammer. The extremely critical texture of wool fibers within the hammer are altered often resulting in compromised tone.
To keep a piano at it’s best, regulate the environment in which it lives. Indeed the piano responds to changes around it. Light, heat, cold, dryness, moisture and any change to any of these will be immediate at the piano. Extreme conditions and fluctuations cause damage to the piano.
The best thing you can do to the great benefit of your piano is to monitor the conditions near your piano and try to create conditions which are most comfortable for you and a fine instrument. Avoid having the piano bathed in direct sunlight or near heat sources. Hot air from floor vents, close proximity to radiators and direct cold air from air conditioners are not good for the piano. Pianos in schools, churches, clubs, halls, hotels and other places do poorly when the environment is changed by altering heat, A/C or by moving pianos around frequently.
If you are interested in keeping your piano healthy and in making your tuner or technician also very happy to see you, control the environment at the piano as carefully as you can. Your tech can continue this conversation at length and will be happy to.