What Is A Pitch Correction?

A pitch correction, also known as pitch raise or pre-tuning, is a preliminary piano tuning performed before a regular tuning. This process adjusts the overall tension of the piano’s structure and can be one of the most challenging procedures for a piano.

Typically, a well-maintained piano doesn’t need a pitch raise. However, significant changes in temperature, humidity, or placement, along with loose tuning pins or heavy playing, can cause the pitch to deviate significantly. If it’s been several years since your piano was last tuned, multiple pitch raises might be necessary to restore long-term tuning stability.

Over time, repeated swelling and relaxing of the wood causes a piano’s pitch to sag from its original levels of tension. The tuner must carefully stretch the piano’s strings to precise tension points to adjust the pitch before the final tuning.

Is Pitch Correction Really Necessary?

On other string instruments, typically one tuning will suffice. But the piano is unique in that it has over 220 strings, each under 150-200 lbs. of tension, totaling 18 to 20 tons. This immense pressure affects the soundboard, bridges, and cast iron plate. Strings have memory, somewhat like a rubber band- and have a tendency to want to return to their previous tension. Thus, a string will quickly stretch and drop in pitch if raised even slightly too high. What’s more, the excessive pressure added to the sound board during this process will cause strings that have just been tuned to sag even further in pitch.

To compensate for this phenomenon, technicians must use what is known as “overpull”: a method by which exact measurements of additional string tension must be calculated in order to mitigate the inevitable drop in pitch after tuning. Even this technique has its limitations, which is why more than one session is sometimes necessary.

There are many other factors at play when determining a piano’s pitch stability; the age of the piano, the age of the strings, variations in humidity and weather, the condition of the pin block, etc. All of these will guide a technician when diagnosing the amount of care required.

Old pianos, especially those which have not been on a regular tuning schedule, can be at a disadvantage. But even brand new strings must stretch an extreme amount before becoming stable. In fact, a new piano must undergo several tunings over a period of weeks or months before it is sold, ensuring that it is stable before a customer ever sees it.