FREQUENTLY ASKED QUESTIONS
This information is take from the Technical Bulletins from the Piano Technicians Guild
Used with Permission
BASIC INFORMATION ON PITCH RAISING
Your piano, just like every piano, is designed to sound its best when tuned to A-440 (the A above middle vibrates 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 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 aways from home. Though your home is no longer filled with music, it’s important to remember you 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 a procedure technicians call a “pitch raise.”
Why has my piano become 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 pianos 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 affect the others. Therefore, a piano must already be fairly close to standard pitch 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 in 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.
INFORMATION ON 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 level affect my piano's tuning?
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 will only stay in tune as long as the relative humidity level in the air surrounding 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.
What is relative humidity?
Wood swells and shrinks in response to changes in the relative humidity of the air around it. Relative humidity 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 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.