Why pianos go out of tune.

Influenced by the acoustical qualities of the environment in which the piano or grand piano lives, the sound of the instrument is produced by vibrating steel strings, which vibrate via a bridge to the soundboard. The vibrating soundboard surface stimulates a large number of air molecules and the sound becomes audible to our ears. The sounds the instrument produces have certain frequencies (number of Hertz) that determines the height of the sound (pitch).


All wood shrinks and swells with humidity changes... even your piano! In the wet season, when humidity levels in the air are higher, you may notice that some of your drawers or doors stick. This is because the woods absorb moisture from the air and swell in the wet season, while they shrink in the dry season.


The rounded soundboard is the single largest piece of wood in your piano. The bridges of your piano are joined to the soundboard and support the strings. As the soundboard and bridges absorb moisture from the air, they swell, causing the strings to be pushed up to a higher string angle. This puts additional tension on the strings and the pitch is too high (sharp) in the tenor, mid-range and extreme treble strings, causing your piano to sound out of tune.

In dry weather the reverse happens. However, as the strings in your piano vary enormously in length, thickness and tension, they never retune themselves perfectly and your piano remains out of tune.

Remember, it can be hot and dry, cold and dry, hot and wet or cold and wet, depending on the climate zone you live in. Thus, temperature changes have less effect on swelling and shrinking of wood.

To see what soundboards look like, go the the link Repairs & Restorations.

Glued wooden joints become loose in your furniture and piano when the air in your home becomes dryer from seasonal changes or from winter heating. Hundreds of interrelated action mechanism parts loose their alignment with each other and the strings as hundreds of screws become loose. Over time, constant changes in humidity levels, with the corresponding shrinking and swelling of

the soundboard, will damage the integrity of the soundboard. You will see this damage in the form of cracks in the soundboard. (The photo on the right shows the cracked and flattened soundboard of a Bechstein grand piano with the strings and frame removed).

Tuning pins and bridge pins are constantly under high stress from string tension. String tension varies between approximately 75kg and 150kg per string and the total string tension on a piano can be in the vicinity of 16,300kg (16.3 tonnes) to 27,200 kg (27.2 tonnes).

As the pinblock and bridges absorb moisture in periods of high humidity, it swells, crushing the wood fibres against the pins. In dry periods, the wood shrinks away from the pins, loosening the pins, causing the pins to lean over and eventually the pinblock and bridges to crack (photos left and right). When pins are loose, they no longer have a snug and tight fit and have lost their resilience. This deterioration compromises tuning stability and causes the piano to go out of tune sooner than it normally would.

The strings in a piano are responsible for producing the musical sounds. With exposure to high humidity levels, strings become rusted and corroded. Sound distortion is a result of loose bridge pins, other faulty string termination points, rusted strings and worn hammers.

The art of Tuning

Piano tuning is physically and mentally hard work and is very skilful work. It requires very careful listening and intense concentration. The tuner compares one pitch to another and adjusts the tension of strings so they sound pleasant when played in combinations. Pitches of nearly coincident frequencies produce beats, or pulsations in the loudness of the tone. When comparing pitches, you listen for beats and either eliminate them or adjust their speed. To be able to hear the beats properly, make very fine and accurate adjustments and do the best possible tuning, it is all- important and necessary that there is absolute silence. All kinds of noises may interfere with the hearing of the tuner and break the concentration. Noises from a radio, television, kitchen, dishwasher, house cleaning, other tradesmen, outside traffic, lawn mowing etc. are obviously detrimental to the quality of tuning. Noises such as talking, ringing telephones, barking dogs, the chimes of a clock are also very difficult conditions to work under. Even a ceiling fan, or just walking around the room in which the piano is being tuned, creates air turbulence and sound distortion. It is imperative that a suitable noise-free time is arranged, enabling the piano tuner to perform at his best, thus avoiding prolonging the work and arriving late for the next appointment.

Please be prepared for the arrival of the piano tuner/technician.  Please clean the keys and remove all your photos and other items off your piano.

 Tuning frequency

Piano manufacturers recommend four tunings per year because there are four seasons in a year.  But people have a habit of neglecting things and push the service frequency to the bare limit or skip services all together.  Only until things fail to work or the piano sounds like a "honky tonk" do they call a tuner/technician.  A piano should be tuned at least two times per year.  Tuning a piano less than twice a year makes it impossible to play on an in-tune piano all year round and maintain its proper pitch. When tuning has been neglected for an extended period of time, the strings in the tenor, mid-range and extreme treble have often dropped in pitch much more, in comparison with the bass strings which have also dropped in pitch.  The string tension has decreased so much and unevenly, that the soundboard and bridges have warped out of shape, placing tremendous strain on wood and glue joints, risking severe damage.  If your piano is too much "off-pitch" due to a lack of tuning or humidity fluctuations, the tuner will need to adjust the string tension to achieve proper pitch before he/she can even begin to do a fine tuning.  Pitch adjustments are time consuming and you don't save any money by delaying or skipping tunings.  Pianos are big and heavy, but are nevertheless very delicate, sensitive and precision instruments.  Good quality instruments are costly investments and are definitely worth looking after and preserving.  Tuning is indisputably important. There is a misconception that when a piano is not played, it will not need tuning or servicing.  Even if it is not played at all, you should have it tuned once every year to prevent the soundboard and bridges from warping and cracking.

An out of tune piano can also affect a person's learning in terms of developing good aural skills.  A piano with an action mechanism that shows wear and is in need of regulating will also affect a person's learning in terms of developing good technique, even touch and even tone volume.  A piano with uneven action and keyboard regulation will have an uneven touch, which means an uneven tone.  The touch weight of the keys are often too heavy.  Those pianos are not "played" with, but are "fought".  There is a danger here of developing bad habits to make up for the short comings of the performance of the piano.  On the other hand, a beautifully tuned piano together with an action mechanism that is well maintained and regulated on a regular basis will be a joy to play, as it is much more pleasing to the ear and it will respond to the pianist's fine emotional musical expressions from the softest pianissimo to the loudest fortissimo.  It will motivate and inspire the player to further explore the piano and its repertoire.  Regular regulating and tuning of your piano will help to maximise its value for potential future trade-in or sale.

Tuning stability

It is important to realize that pianos that have drifted radically off-pitch will usually go out of tune quickly after they are tuned. Those pianos require several tunings within a short space of time to settle down, as the warped soundboard and bridges and stretching strings need to restabilize.  In comparison, you would not expect an overgrown two feet tall grass "lawn" to look like a bowling green after one cut.  A piano that is tuned every six months will have a greater tuning stability than a piano that is neglected for two years and is tuned three times in one month.  Additional time and tunings will be required when a piano has been moved to another climate zone, home or even a different room. Pianos are very sensitive to changes in relative humidity which occurs continuously all day, every day.  A perfectly tuned piano can be out of tune within one hour if the relative humidity has changed too much.  Any acoustical stringed instrument will never stay perfectly in tune for long.  This is why every acoustical instrument is tuned every time it is played, except a piano.  For some unknown unreasonable reason many people expect a piano to stay in tune for a year or longer.  A piano has about 235 strings which vary tremendously in thickness, length and tension, and is far more complex to tune and keep stable than any other instrument.  If a brand new piano in excellent structural condition, is radically off-pitch and/or out of tune, it will take a number of tunings to get the piano to stay on pitch and keep it in tune.  If a fairly young aged piano or older piano has loose tuning pins, loose bridge pins or has cracks in the soundboard, the tuning will be less stable, unstable, or is simply untunable.  Bridge pins on top of the bridge can also become loose from frequent swelling and shrinking of surrounding wood.  When a bridge pin is loose, the sound quality of that string is dramatically reduced and fine tuning that string has become impossible.  The string is under high tension and pushes against the loose pin. The loose pin vibrates inside the wood and causes the string to produce different pitches (a vibrato like tone). Tuners call this a "false" or "self beating" string.  There are three strings to the note (trichord) in the tenor and treble.  If one, two or even three strings in the same note have a beat of their own, that note cannot be tuned to a perfect unison.  Self beating strings cannot be eliminated by tuning and your piano will never sound as good again as when it was brand new, unless the bridge is repaired.  This is usually a costly exercise and is only done if the piano is worth restoring. To avoid loose bridge pins and self beating strings in the first place, or prevent the bridge from cracking, have a Climate Control System installed inside your piano, preferably from the day it was brand new.  High string tension constantly pushing against the bridge-pins will cause the bridge to crack over time if the humidity inside the piano is not constantly kept stable.  Cracked bridges destabilize the tuning even more.

Please go to our link "The environment" to learn how humidity affects pianos.

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