How Piano Tuning Works: An Insider’s Guide

From the outside, a piano seems like a single, monolithic instrument. Under the lid, however, is an orchestra of more than 200 strings pulling at a cast-iron frame with twelve tonnes of tension. Each note is actually a small choir of strings, and keeping that choir harmonious is the art and science of piano tuning.

## Why do pianos go out of tune?

The pitch of a stringed instrument depends on string tension, length and mass. On a piano, the strings are wrapped around tuning pins, and tension is adjusted by turning these pins. Anything that changes the tension changes the pitch, and there are many culprits. Humidity affects the soundboard, causing it to swell or shrink—when humidity rises, the soundboard expands and the strings are pulled sharp; when it falls, they slacken and the pitch drops. New strings gradually stretch, old tuning pins can loosen, and enthusiastic playing can knock strings slightly out of tune. Because of these factors, manufacturers generally recommend tuning a new piano four times in its first year and twice a year thereafter.

## What is tuning?

At its simplest, tuning means adjusting the tension of the strings so that the musical intervals between them sound pleasing. Pianos are usually tuned to equal temperament using the pitch A = 440 Hz (often written A440) as a reference. In equal temperament, each semitone is the same size, allowing music to be played in any key without the intervals becoming wildly out of proportion.

However, tuning is not as simple as dialling every string to a preset frequency. A piano string vibrates as a complex of harmonics rather than a single tone. When two strings are close but not perfectly aligned, their overlapping harmonics beat against each other; you hear a gentle wobble in the sound called beating. Tuners listen for those beats and adjust tension until the wobble speeds up or slows down to the desired rate. Eliminating beats in unisons (multiple strings for one note) is essential to a clean sound, but slight beating is intentionally left in larger intervals to create the equal temperament.

## Tools of the trade

A traditional tuning kit contains:

– **Tuning lever (hammer)** – a wrench designed to grip tuning pins so the technician can turn them. A good lever makes very small, controlled adjustments much easier.
– **Rubber mutes or felt strips** – used to silence unwanted strings when tuning unisons. Mute the outside strings so you can focus on one string at a time.
– **Tuning fork or electronic tuner** – an A440 tuning fork provides an absolute reference pitch; many professionals also use modern electronic tuning devices that analyse the harmonics of each string.
– **Felt temperament strip and metronome** – a felt strip allows you to mute several strings quickly to set the temperament, and a metronome can help learners count the beat rates (7, 8 and 9 beats per second) used in aural tuning.

## Step‑by‑step tuning

### 1. Set the temperament

The tuner begins in the middle of the keyboard—usually between F3 and F4—because the strings here behave most predictably. This region of twelve notes is called the temperament octave or temperament for short. First, the outer strings of each unison are muted with a felt strip, leaving a single string per note.

Next, one reference note (commonly A4) is tuned to a tuning fork or electronic device at 440 Hz. Then the remaining notes in the temperament are tuned relative to A4 using intervals. Many technicians prefer using thirds and sixths because their beat rates of 7–9 beats per second are easier to judge than the slower beat rates of fourths and fifths. The goal is to create an even progression of beat rates across the octave—a characteristic of equal temperament.

### 2. Tune octaves and unisons

Once the twelve-note temperament is stable, its pitch relationships are copied across the rest of the keyboard. The technician tunes octaves upward and downward from the temperament region, checking fifths, fourths, thirds and sixths along the way to confirm the beats progress evenly. Each note has two or three strings; after one string has been tuned, the mutes are repositioned and the remaining strings are tuned in unison until all beating is eliminated.

### 3. Apply the stretch

Because real piano strings are stiff, their higher partials are slightly sharper than ideal theoretical harmonics. If octaves were tuned exactly 2:1 (perfectly double frequency), chords spread over several octaves would sound dull. Tuners therefore stretch the octaves: treble notes are tuned slightly sharper and bass notes slightly flatter so that the instrument sounds harmonious over its entire range. The amount of stretch is judged by ear and varies from instrument to instrument, making tuning as much art as science.

### 4. Final check

A good tuning ends with a general review. Tuners recheck unisons, listen for lingering beats and make micro-adjustments to bring everything into balance. Modern electronic tuning devices can help confirm the overall tuning, but experienced aural tuners rely on their ears for the final verdict.

## Should you tune your own piano?

Tuning is a skill learned through practise and training. While a handy musician can learn the basics, working on your own instrument does carry risks. A poor adjustment can break a string or damage the pin block, and inexperience makes it easy to chase your tail around the keyboard without achieving stability. Most piano owners prefer to book a professional tuner twice a year—particularly because an experienced technician will also spot other maintenance issues such as loose screws, worn hammers or buzzing strings.

For anyone fascinated by the craft, there are excellent courses and resources available. Even if you never pick up a tuning hammer, understanding what the technician is doing will give you a deeper appreciation of the engineering hidden behind your keyboard. At Montague Pianos we make sure every instrument is prepared and maintained to concert standard, trusted by educational institutions, composers, and the Royal Ballet. That way, your piano remains a reliable partner from the quietest practise to the grandest performance.