Piano Care, the how, whys and wherefores…

Why does a Piano slip out of Tune?

The following short statement was prepared by William Braid White, Mus. D. for his book, Piano Tuning and Allied Arts, a number of years ago. It was later adopted by Steinway and Sons, of New York, at Steinway Hall, and for the use of Steinway dealers. It is reproduced with the permission of Steinway & Sons, and because the facts presented are likely to be very useful to professional tuners, who so often have to make clear to owners of pianos the ins and outs of a question easily understood by technical men, but very mysterious to the laity.

In order to understand why a piano goes out of tune, it is first necessary to remember that the whole instrument is always under a varying stress. The two-hundred-and-thirty odd strings are stretched at average tensions of from one hundred and fifty to two hundred pounds apiece; so that the iron plate, together with the heavy wooden framing carries a strain totaling from eighteen to twenty tons.

Now, this stress is not constant, for the reason that the steel wire is highly elastic. The soundboard is merely a thin sheet of spruce wood averaging three-eighths of an inch in thickness. If it be properly constructed, the whole board becomes something like a highly elastic spring. The more elastic it is, the freer and more agreeable will be the tone emanating from the piano. 

Your Piano’s sensitivity to Humidity:

Unfortunately this very construction is extremely sensitive to all changes of temperature and barometric pressure. Thus, in summer time, through out the greater of the country there is much moisture in the air most of the time, and rain is frequent. Wood, under these conditions, swells up, nor will any kind of coating protect a wooden soundboard from these influences. On the contrary, when the heat is on during the colder months, the air in the rooms becomes much drier, owing to the evaporation of moisture, and failure to keep on hand open vessels of water, flowering plants or other moisture retainers or humidifiers.

Consequently the moisture in the soundboard rapidly passes off, the board shrinks, the strings slacken down, and the pitch drops.

Continual/Frequent Variations in Conditions:

Now it is perfectly evident that even where conditions are not extreme, and even in climates which have only a comparatively short range, this process is continually going on.

Every change of a degree in temperature, or of one-tenth of an inch in a barometer, has its effect. The soundboard of the piano, then, is always slowly rising and falling through short distances, and constantly, therefore, suffering variations in its ability to hold the strings up to proper pitch.

On the other hand, if the piano be neglected, and unless it be tuned at least once every change in season, say four times a year, during Spring, Summer Autumn and Winter, it will not stand in tune. 

The Truths: Can/Does a Piano really “Stay/Stand in Tune?”

From the layman’s standpoint, four tunings a year should be sufficient. The tuner knows however, that if he had time to tune his own piano as often as his ears tell him, he would tune it once a month at least.

From a strictly scientific point of view, it is probably true to say that no piano ever made has stood in tune, without a drop or a rise for more than twenty-four hours, unless it were maintained at constant temperature, and under constant barometric and hygroscopic conditions in a laboratory. 

Considerations of the Neglected Piano…

So much then for the frequency and need of tuning. If a piano is neglected, if it be allowed to go through from one season to another, say, from Spring to Winter, without tuning, it will probably at the end of that time be considerably lower in pitch that it was originally. It will have gone through a rise, followed by a fall, and the fall will be greater than the first rise.

No matter what any salesman may say, no matter how finely the piano may be made, no matter, in fact, what the physical circumstances or the price, or the domestic conditions may be, there is no such thing as a piano standing month after month in tune. The better the piano, the more frequent and careful tuning it should have.

A fine piano is a work of art. Therefore, to treat it roughly, carelessly or negligently is to commit a crime against a beautiful piece of expensive craftsmanship. To pay a lot of money for a fine piano and then allow it to go to ruin for lack of expert care is not merely aesthetically wrong-it is bad business.

Humidity Control:

Your piano is made primarily of wood, a versatile and beautiful material ideal for piano construction. However, being made of wood, your piano is greatly affected by humidity. Seasonal and even daily changes in humidity cause wood parts to swell and shrink, affecting tuning stability and touch. Extreme swings in humidity can eventually cause wood to crack and glue joints to fail.

Other materials in your piano also are affected by changes in moisture content in the air. The many felt and leather parts in your piano’s action can change dimension, affecting regulation and friction, or stiffness of the touch. Very high humidity can even create condensation on metal parts such as strings, tuning pins and hardware, eventually causing them to rust.

How does Humidity or the Lack of Humidity affect my Piano’s Tuning, Stability and Structure?

Swelling and shrinking of the piano’s soundboard is the most immediate and noticeable effect of humidity change. The soundboard, a sheet of wood approximately 3/8 of an inch thick, is made with a slightly crowned shape. The strings pass over the soundboard and are connected to it by a wooden piece called a bridge. The upward crown of the soundboard presses the bridge tightly against the strings.

As the moisture level in the soundboard increases during periods of high relative humidity, the crown expands and pushes the bridge harder against the strings. The strings are stretched tighter and the piano’s pitch rises. Because this increase in crown is greater in the center of the soundboard than at the edges, the pitch rises more in the middle octaves than in the bass or treble registers.

During periods of low relative humidity the soundboard shrinks, reducing the crown and decreasing pressure against the strings. The pitch drops, again with the greatest effect noticeable in the center of the keyboard. When relative humidity returns to its previous level, the average pitch of all the strings will return to normal, although the exact pitch of individual strings will be slightly changed from their original settings. Thus, a piano only will stay in tune as the soundboard remains constant. Extreme humidity changes require making greater changes in string tension to bring the piano into tune. This upsets the equilibrium between the string tension and the piano frame, and the piano never becomes stable.

Sadly these swings in the environmental humidity can and often do, reek significant havoc and damage to your piano. It’s soundboard, the heart of the piano, may/will develop cracks, some so significant that they will warrant replacing the soundboard in order to maintain the tonal integrity of the piano. The pin-block can also develop cracks and weaken to the point that it will no longer grip the tuning pins, which allow the piano to be tuned, and hold its pitch, and this is only the beginning of the destruction that can be caused by environmental humidity swings. 

The case itself can even dry out over time, causing the veneers to lift and crack due to the influx and then drying out with these changes.

From the PTG:

How does humidity affect my piano?

Extreme swings from hot to cold or dry to wet are harmful to your piano. Dryness causes the piano’s pitch to go flat; moisture makes it go sharp. Repeated swings in relative humidity can cause soundboards to crack or distort. Extreme dryness also can weaken the glue joints that hold the soundboard and other wood portions of the piano together. Moisture may lead to string rust. A piano functions best under fairly consistent conditions which are neither too wet nor dry, optimally at a temperature of 68 degrees F and 42 percent relative humidity.

Using an air conditioner in humid summer months and adding a humidifier to your central heating system will reduce the extremes of high and low humidity. Room humidifiers and dehumidifiers, as well as systems designed to be installed inside of pianos will control humidity-related disorders still further. The PTG technical bulletin on humidity control discusses this topic in further detail.

What is relative humidity? 

Wood swells and shrinks in response to changes in the relative humidity of the air around it. Relative humidity (RH) is the amount of moisture contained in the air, compared to the maximum amount of moisture that it is capable of holding. The moisture content of air is affected by weather as well as conditions and activities within the home, while the moisture-holding capacity of air varies with temperature. One way of thinking about RH is that it is a measure of air’s tendency to absorb or release moisture to its surroundings. Thus when the RH of air in a room increases, moisture will tend to transfer from the air to wood and other absorbent materials in the room. When the RH of air decreases, moisture will transfer from other materials back into the air. The RH of the atmosphere is always changing by the hour and, more dramatically, with the seasons. Consequently, the wood and felt parts in your piano are constantly changing dimension as they absorb and release moisture.

Since RH depends upon the temperature and moisture content of the air, it is not possible to maintain a constant RH by controlling room temperature alone. In fact, maintaining an even temperature while moisture content varies will cause RH to change.

What can be done to minimize humidity problems?

Keeping the humidity level around your piano as constant as possible will help it stay in tune longer as well as slow such damage as soundboard cracks, loose tuning pins, and glue joint failures. The first and simplest precaution you can take is to position your piano away from areas where it would be exposed to extremes of temperature and humidity such as heating and cooling vents, stoves, doors and windows. Direct sunlight is especially damaging. If your home is not well insulated, an interior wall is preferable to an outside wall.

Controlling the humidity within the home is another step you can take to preserve your instrument. In most areas of the country the relative humidity is very low during the cold winter season, and very high during the spring and summer. In other areas these humidity cycles are reversed. Wherever you live, you have probably noticed the symptoms of low RH (shocks from static electricity when sliding out of a car or after walking across carpet), and the signs of high RH (limp, soggy-feeling newspapers and sticking doors). To monitor RH changes in your home, you may wish to purchase a moderately priced wall hygrometer available from most instrument supply companies or electronics stores.

Use of a room humidifier during dry seasons will help somewhat. However, too much moisture added to a room during winter months can cause condensation to form on cold surfaces such as windows, eventually causing mildew, rot, and, in extreme cases, damage to the building structure. During the humid season de-humidification is needed. If your humid season is winter, keeping the home evenly heated will help. However, humid summer situations require much more elaborate de-humidification systems. Unfortunately, it is seldom possible to adequately control the relative humidity of a piano by controlling the room environment alone.

A very practical and effective answer to humidity problems is to have a humidity control system installed in the piano itself. These systems consist of three parts: a humidifier for adding moisture to the air, a dehumidifier for eliminating excess moisture, and a humidistat or control unit which senses the RH of the air within the piano and activates the system to add or remove moisture as needed. These systems are designed to maintain the RH of the air within the piano at the ideal level of 42%. The components are installed out of sight, inside the case of a vertical piano or under the soundboard of a grand. They are easy to maintain, and can be installed by your piano technician. (We recommend and stand behind the “Piano Lifesaver, DamppChaser Climate Control System.”)

How will humidity control benefit my piano?

While not eliminating the need for regular piano maintenance, humidity control will allow more stable tunings by reducing the radical pitch changes your piano may experience
through the seasons. When your piano stays closer to its correct pitch level of A-440 (A=440 cycles per second), your technician does not have to perform a large pitch raising or lowering procedure prior to fine tuning. Thus, a balance of forces is maintained between the strings and the frame of the piano, allowing more accurate and stable tunings to be done.

In addition, a stable environment will help to preserve your piano through the years. Wood parts, glue joints, metal parts and your piano’s finish will all last longer if not subjected to excessive humidity swings. Maintaining the correct environment will preserve your piano investment for a lifetime of enjoyment.

The Need /Value of a Pitch Raise and When is it warranted:

Your Piano, just like every piano, is designed to sound its best when tuned to A-440 (the A above middle C vibrates at 440 cycles per second), the international pitch standard. It has been designed to perform at a specific tension, and when strings stretch beyond, or drop below this tension, pitch adjustments are required to bring it back to A-440. It’s important to remember that maintaining your piano at standard pitch allows you to play along with other instruments which are all designed to this same standard. Through neglect, pianos may deviate from this standard, making them unsuitable to play with other instruments and causing them to lose market value. In addition, lower pitched instruments can compromise the pianist’s ear training.

It’s important to note that pianos do not go flat or sharp uniformly. Some strings will invariably change more than others.

If I haven’t had my piano tuned regularly, how can I get it back in good playing condition?

After years of regular use, your piano may have fallen silent when the family member who studied music moved away from home. Though your home is no longer filled with music, it’s important to remember your piano is still a living, breathing thing. Its wood continues to expand and contract with seasonal changes in temperature and humidity, and the string tension also fluctuates accordingly. If your piano has gone without tuning for an extended period, its pitch may have dropped far below the pitch at which it was designed to perform. It may require procedure technicians call a "pitch raise."

Why has my piano slipped/fallen out of tune?

Changes take place because your piano’s overall pitch is dependent upon changes in the relative humidity. In some temperate regions of the country, the relative humidity increases in the summer resulting in a higher moisture content in the soundboard and a higher string tension (pitch). In the winter, when heating systems dry the air, the soundboard loses moisture and contracts, causing the pitch to drop. The drop in the winter tends to exceed the rise in the summer, so the net result is a drop in pitch each year that the piano isn’t serviced. In some parts of the country where the cold season is exceptionally long, the annual drop can be considerable. In other parts, mild winters combined with dry summers cause the cycle to be reversed. You can, however, greatly increase the stability of your piano’s pitch by maintaining a relatively consistent humidity level in the room.

Why is a pitch raise necessary?

When the tension of each string on a piano is raised back up to pitch, the additional load on the piano’s structure causes the pitch of previously adjusted strings to change. The only way to achieve a fine, accurate tuning on a piano is to have the tension of all the strings so close to their proper place that altering the tension of one string would not affect the others. Therefore, a piano must already be fairly close to standard pitch in order to be finely tuned.

Wouldn’t it be easier to just tune the piano to the lower pitch?

Tuning to anything other than the international standard of A-440 is seldom appropriate. If a very old piano has been allowed to remain appreciably below pitch for a long time, some strings may break if the piano is restored to A-440. Your technician will advise you as to whether repeated tunings will correct the problem, or if the piano should be completely restrung or rebuilt.

If a piano has dropped in pitch, the drop will not be even. The middle (tenor) section of the piano usually drops most along with the high treble section. The bass section tends to drop least. Consequently, a piano that is tuned to a pitch that is below the international pitch standard would have to have significant adjustments made to the tension of every string, resulting in an unstable tuning. It’s much more reliable to bring the piano up to standard pitch and then to proceed with fine tuning.

How far from the standard pitch must a piano be before a pitch raise is necessary?

Pianos that have been subjected to severe changes in humidity routinely need pitch raises before a fine -tuning can be achieved. For example, if A-440 has drifted only two cycles per second to A-438, a separate pitch raise is advisable. Most recreational musicians would want to have their pianos tuned before the pitch drops that far. Even if you aren’t bothered by a slightly out-of-tune piano, it’s best to tune the piano on a regular basis to avoid tuning instability and the extra cost of a pitch raising procedure.

Like your car, your piano is a major investment which deserves to be protected by regular servicing, which can head off preventable problems in the future. But most importantly, your piano will sound its best and give you and your family the most pleasure when it is tuned regularly and kept in proper playing condition.

Basic Knowledge:

Standard/Concert Pitch in the USA is generally, a–440-a–441

Any pitch below a–438 considered significantly flat and any pitch above a–441.5 significantly sharp.

Soundboard: Spruce and is where the sound emanates from.

Pin-block: Laminated Maple, drilled, holds all of the Tuning Pins, which along with the strings, allow the tuning.

Care & Maintenance of Your, "Fine Piano."


Terry L. Greene, R.P.T.

Fine Piano Services & Restorations since 1976