Playertechs

Player Piano Technicians

©2012 - Wayne Johnston

Why does a piano go out of tune?

For a piano to be in tune, the strings must be pulled to exactly the right tension so that they will vibrate with exactly the right number of vibrations per second when struck by the hammer. Most notes of the piano have three strings, all of which must vibrate exactly together in order to sound in tune. Even the slightest alteration of tension of a string will create a dissonance.

A piano has approximately 240 steel strings. Each one is stretched to a tension of around 150 pounds. The strings are always trying to eliminate the tension on them, but they are held tight by a rigid cast iron plate and the sturdy wooden case of the piano. So you could consider the piano to be a continual battleground between the strings, which are trying to loosen the tension, and the case and plate, which are trying to hold them tight. Overall, there are 18 tons of tension on all the strings of a piano, so the battle is intense. If a plate should break, the piano could collapse like an accordion.

Every year the strings win a little in the battle. Typically, the tension on the “A” string above middle “C” drops enough in one year to lower the pitch from the International Standard* of 440 vibrations per second (cps) to about 439 cps. This drop in the tension is one reason a piano goes out of tune.

When the hammer strikes the strings it loosens some of the tension and a drop in pitch will occur. Naturally, the harder the piano is played and the frequency of playing also contributes to the piano going out of tune.

The weather is also a factor. The vibrations of the strings are transferred to the soundboard through the bridges. When the wood of the soundboard and bridges shrinks in dry weather, the upward push of the bridges on the strings is less, and the strings get looser. Conversely, in wet weather the bridges and soundboard swell, pushing up harder on the strings and tightening them. Thus normal weather changes can cause a piano to go out of tune by changing the tension on the strings. A piano may actually go back in tune after a rain or a Santa Ana dry spell.


What is a Pitch Raise?

Piano strings, like the strings of all stringed instruments, are always getting looser. On the average, the “A” string above middle “C” will loosen from 440 vibrations per second (cps) to 439 cps over the course of a year. The next year it will typically drop to 438 cps, and so forth. Once that “A” drops to 438 cps, the tuning will be considered a pitch raise.

Your piano will need a second tuning within a few months after it had a pitch raise, but this varies with the piano, and with the type of use that it gets. Your tuner will recommend when the next tuning should be. Most pianos will need a pitch raise if they are not tuned periodically. You should establish a regular service plan to have your piano tuned at least once a year.


What is Regulation?

Regulation is a technical term used to refer to the adjustment of the touch of a piano. It is a series of actions which the technician performs in a sequence to restore the proper feel in playing.
When a piano leaves the factory, the adjustment of the touch is presumably correct; from that time on, it will go progressively more out of adjustment. This is inevitable, because the felt parts inside of the mechanism, which are designed to cushion the contact points, begin to wear and compact. The manufactures know that this will happen, so they have designed in many screws and buttons that can be adjusted to compensate for the wear. Where there are no screws or buttons, the felt parts can be replaced. All of these procedures are part of regulation.

There are three important adjustments which you should know about: 1. The hammer blow, which is the distance the hammer has to travel to reach the strings (about 1- 7/8 inches), 2. The key dip, which is the distance the key travels down when depressed (about 3/8 inch), and 3. The let-off, which is the point where the hammer is released to travel freely to the string and bounce back (1/8 inch from the string). All three are important and your piano will not play well if any one is out of adjustment. There comes a time in the life of every piano when the parts become so worn that there is no point in regulating and replacement is necessary.


*International Standard Pitch is a standard like the inch or the pound. What it means is that the “A” above middle “C” is supposed to vibrate 440 times per second. This was decided in 1936 by the International Association of Standards. Pianos should be tuned to this standard. This is done by matching a tuning fork or an electronic tuning instrument to the “A” string above middle “C”.