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Tuning is the process of making minute adjustments to the tensions of the strings in a piano so that musical intervals between the strings are properly aligned.

To do this, a professional piano tuner tunes each string by matching the frequencies of corresponding harmonics to that of the principal frequency at which it vibrates. This is a complex, psychoacoustic process that involves listening for and eliminating tiny interference patterns called beats in the soundwave. Read this first!

String Tension

In piano tuning, the string tension is the amount of force applied to each of the strings that cause them to vibrate. This force determines the frequencies and pitches that are produced.

During tuning, the tuner will make small changes to the string tensions to ensure that all the strings are at an approximate correct tension. This allows them to produce a set of pitches that are a standard distance apart.

Another benefit of keeping the string tensions consistent across all the strings is that they can help to give the piano a more even spread of tension on its pins and frame.

In terms of sound production, the higher the string tension, the more complex vibrations are produced by the string, leading to a brighter and fuller sound. This was a major trend through the 19th century and is what we associate with the timbre of today’s acoustic pianos.

Key Regulation

The key regulation is the process of making all of the parts inside your piano function in concert with one another. It can be the difference between a piano that plays softly and loudly and an instrument that has clicks, noises, or unevenness in its tone.

When a piano is properly regulated, the keys and the hammers strike each string squarely. The hammers are also shaped to remove grooves and restore their original rounded shape, and the action is aligned to the strings to make each note sound as evenly as possible.

The goal of regulation is to make the tuned piano’s touch and sound consistent across all notes, allow it to comfortably achieve the widest possible range of dynamics, and make the keys responsive to even the most rapid or subtle motions of the player. Regulation involves adjustments to let-off, the point when the hammer disengages from the jack and flies freely; drop, how far the hammers fall back after let-off; and repetition springs in a grand piano, which controls how much a hammer strikes repeatedly without lifting a key.


In order to properly sound a piano, the hammer must instantly rebound from the string(s) it strikes. This action is a complex process that can only be accomplished with precision.

When a key is pressed down, the hammer must be placed on the string at just the right height so that it can quickly strike the string(s). The hammer must then be repositioned and reset for another blow.

If the hammer is not correctly positioned, it can bounce back and forth against the strings, creating a muffled sound. This can cause the strings to vibrate, resulting in poor tuning stability.

Dampening is a very important aspect of piano tuning and must be addressed by a professional tuner. A poorly-maintained instrument may not be responsive to pedaling and will eventually become unplayable.

Damaged wood, worn action parts, and improper regulation are all potential causes of dampening. In addition, the metal parts of a piano can begin to rust when exposed to unstable humidity levels and temperatures.


In music, inharmonicity is the degree to which overtones (or partials) of a note depart from whole multiples of the fundamental frequency. A violin string, for example, has overtones that are exact multiples of the fundamental frequency, while a piano string is more complex.

The inharmonicity of a piano string depends on its length and stiffness, which affect the way the string vibrates. Shorter and thicker strings have higher inharmonicity than longer and thinner ones.

Tuners use inharmonicity to determine how far an octave should be stretched. This stretching enables the octave to be tuned to a coincident partial of a reference pitch, instead of the lowest one.

This tuning is referred to as equal temperament. However, it can be difficult to achieve a perfect temperament, particularly as the octave is stretched. This is because of both physical and psychoacoustic factors that may interfere with the tuner’s ability to tune the octave accurately. Check this helpful information.