TUNING INSTABILITY



In speaking to our customers about what causes a piano to go out of tune, the most common subject is the weather. A change in temperature will have little or no effect on the tune of the instrument except that most temperature changes are directly coupled to a change in humidity. Humidity change is the major factor when pianos are tuned two or more times a year.
The next most common factor is string stretch. It takes very little stretch, as we all well know from what a new string does, to make a piano sound horrid. Several years of tunings are needed to get all the stretch out of new strings. The newer pianos seem to go out because of settling of the structure as well as the stretch of the strings, but I have no proof of that.
Time itself, with the changes of weather, string stretch and structure, all cause the tuning to slide downward.
Hard playing and especially hard hammers will knock out the tuning of even the best tuner and the best piano.
One factor that seems to be rather neglected is the degree of sensitivity of the client. Some pianists are on the phone the instant the piano thinks about going out of tune, others can let the instrument go for ten years and not know the difference.
After the piano is settled in and the weather, stretch, age, time and customer demands are compensated for any real problems of the instrument itself can be considered.
One common cause of tuning instability is pinblock-back separation, where the pinblock is being pulled away from the back posts of uprights by the tension of the strings. This is most easily spotted by looking at the top of the assembly or from the bottom of the block. When the sides begin to separate from the back a weak piano plate and back can flex more than planned by the designers; tapping with the knuckles along the side will produce a hollow sound where the glue has failed.
A good number of pianos were produced with aluminium / magnesium plates that over extended periods do not have the rigidity and stamina of cast iron. This is a chronic problem without any real solution for that instrument.
When the smaller pianos were in their developmental stages, many of their unique problems were yet to be solved. One of which was determining the minimum weight and the structural rigidity for long-term integrity. Some of these early instruments tend to be unstable because of weakness and, of course, because of advanced age.
Closely related to the above is poor or improper scaling. Today there seem to be several instruments available that can yet be improved in this area, but many of the older spinets were and are unstable because of poor scaling.
As mentioned earlier, overly hard hammers can cause a piano to go out of tune because of the severe shocks to the strings, the excessive energy imposed on the friction systern of the strings which helps the strings to ride up on the bridge pins.
If the plate screws and bolts are just a little loose the piano will not be nearly as stable as when they are tight. I know one tuner who tightens the plate screws on every new client’s piano, and every year in the dry season as well. I do it often (once every two years or so) on all my large or critical instruments.
One seemingly insignificant point is one overturned screw in the plate. Any lack of mechanical integrity introduces that much instability. That overturned screw must be replaced or the hole plugged and redrilled.
Along the same lines, if there is a gap, as thin as a piece of typing paper more than three or four inches long between the plate flange and the pinblock of a grand, the stresses placed on the block by the pins will try to force that space to be filled by the block. This should be checked just before the dry season is over. The gaps can be filled with very thin, long maple shims that have been dried out thoroughly so that any moisture in the air will cause the shim to swell after it is installed. Using epoxy will not swell the wood for a tighter fit.
Sometimes the plate is warped or the pinblock is warped so that there is poor contact between the two. This is especially bad in the tuning pin area. If this is the case then a new block is in order or a long fitting process is required.
A pressure bar that has been screwed down too far can make tuning difficult and contribute to string breakage. A close examination of the area should indicate if this is the case. Generally speaking, the pressure bar should be set so that the strings will remain in position no matter how hard they are struck and so that it introduces some friction so that the tuning pin is not doing all the work. On average, fourteen degrees is sufficient.
With time, the strings will conform to the bearing points; the V-bar, pressure bar, bridges, aliquots, agraffes, bearing pins, etc. When you remove an old broken string you can see the bends in it. These bends have to be straightened out, and to some degree, made again when the pitch of a string is changed. In newer pianos the strings make nice curves around these points, but in the older ones they conform and contribute to string breakage, difficult pin setting and to tuning instability.
Excessive friction caused by corroded strings, cape bars, pressure bars, V-bars and bearing bars and occasionally with contaminated bearing felts generally tend to contribute little to the ease of tuning.
Poor hammer technique and poor pin setting are a major source of customer complaints about the tuning instability of their pianos. You should always inform the customers that if there is a problem with the piano to call you immediately. This gives you the chance to go and check the instrument to determine if it is at fault or if you need to retune the piano and concentrate more fully on your approach to the job.
Tight tuning pins and tuning pins that are very high from the plate are difficult to tune, but are not impossible. They just take more time. Coils that are more than 1/8” inch from the plate are in no manner justifiable. These pins should be driven down and properly leveled with tight coils.
The final note on my list is loose tuning pins. How loose is too loose. If you can raise the string to pitch and the tension of the string pulls the hammer around, that is too loose. Also too loose is if you return to a piano after only a few months and find several notes playing major or minor triads.
Too loose is when, even if the pins are tight by measurement (above 75 inch pounds), but they are still a major third low a few months later. These pins may be contaminated with something like oil or silicone which will not allow the wood to grasp the pin for long periods. A new block may be in order.
Even if the block is generally loose, it does not mean that the piano is untunable. I have tuned pianos where every string would turn the pin around, but I could get the block to lock into the pin by raising it to the exact point I wanted, holding steady for just a second, then gently releasing the pressure and gently lifting the hammer off the pin. When the weather changed, it was when I earned my fee.
I prefer pins that are not too tight; I don’t have to work so hard and have some energy left for writing articles.
If it can be made to stay, it is not too loose. European pianos generally do not have pins that are tight, yet they stay and stay and stay and . . .
The degree of looseness is not as important as its staying ability, which is determined by the bearing point angles, the friction across all bearing points, the angle of the tuning pins to the block, the angle of the string to the pins, the texture of the block and the patience of the tuner.
Unless the cause is obvious and until the piano has been tuned at least once by yourself, go cautiously and carefully, as you would like someone to go with your car or TV or with whatever you have a major emotional investment.
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