How Is a Piano Tuned?

Tuning a piano : magic or science?

When I was “only” a pianist and watched a tuner at work, the whole scene seemed almost magical. He would lean over the tuning pins, play notes that sounded off… then suddenly they were in tune.

I used to wonder: How does he do that? Is it a gift? An exact science?

In this article, I’d like to lift the veil on piano tuning. You’ll see it’s not magic at all—but a combination of experience, technique… and a touch of personal taste.

Choosing the starting pitch

Before anything else, the tuner sets the reference pitch: most of the time, the A4 will be tuned to 440 Hz or 442 Hz. Traditionally, this was done with a tuning fork. Nowadays, most tuners prefer an electronic tuning device—more precise, and able to measure the piano’s current pitch.

👉 If the piano is too low (say, if A4 has dropped to 435 Hz or below), a pitch raise will be necessary: gradually tightening the strings to bring the instrument to an acceptable level before it can be stably tuned.

One string at a time

A piano is tuned one string at a time, always in comparison with another string. To do this, we use a felt strip and small rubber or felt wedges (mutes) to silence the strings we don’t want to hear.

The main tool is the tuning hammer, which turns the pins with precision and control.

It’s a highly technical gesture that demands accuracy and a sensitive touch.

Felt strip

Strip, mutes and tuning fork

Mutes and tuning hammer

Listening to the beats

The principle of tuning relies on a key acoustic phenomenon: beats. When two notes are played together, you hear a sort of vibration or “wobble” in the sound. This comes from the interaction of their overtones. The further away you are from harmonic alignment, the faster the beats. As you approach perfect harmony, the beats slow down until they disappear—and the sound becomes pure, steady, and unified.This is the tuner’s compass: learning to hear, compare, and even count the beats per second is an essential skill.

A bit of acoustics

In the equal temperament we use today, each interval is slightly adjusted compared to its natural purity. Fifths are tuned slightly narrow, fourths slightly wide, major thirds noticeably wider, and so on. Some intervals, however, must be perfectly pure, with no beats at all: unisons and octaves. These serve as stable reference points throughout the tuning.

Setting the temperament

Tuning always begins with a crucial step: creating a reference octave—usually from F3 to F4. This is called setting the temperament. This octave will serve as the foundation for tuning the rest of the piano, by successive octaves into the treble and bass. Every semitone in this octave must be placed with great precision, because the smallest error will be duplicated and amplified across the instrument.

All tuners follow the same broad process, but each has personal preferences. Some move upward into the treble first; others go down into the bass. There’s no single “right” way.

Building the temperament octave

Once A4 is set, the temperament octave can be built. Here’s one approach—the one I use:

• Tune A3 as a pure octave from A4.

• Then build the other notes from combinations of fourths and fifths, carefully observing the beat speeds:

  • D4 from A3 (fourth beating at ~1 beat per second)

  • G3 from D (slightly narrow fifth)

  • C4 from G, and so on.

    
    

    At each step, check the thirds, fourths, and fifths to ensure everything fits progressively. In equal temperament, semitones are all equal in size—but to achieve that, each interval has its own specific beat rate: slow beats for fourths, faster ones for thirds, etc.

    This is the most delicate stage of the entire tuning.

    
    

Tuning the unisons

Once the temperament octave is ready, the muted strings are unmuted and the unisons are tuned: the two or three strings of each note are brought into perfect alignment. At this stage, any remaining beats, hiss, or “cat cry” sounds are carefully eliminated. The goal is a pure, perfectly stable tone.

Extending the tuning into the bass

With the reference octave completed, the tuning moves into the bass: semitone by semitone, by pure octaves, checking other intervals (fifths, fourths, thirds) along the way.In the lowest bass, the sound becomes less clear. The “technical ear” gives way to the “musical ear.” Some tuners rely on overtones, others on the sensation of vibration. Personally, I like the bass to be tuned slightly flat compared to theoretical pitch—adding warmth and depth to the sound.

Difference between actual pitch and perceived pitch

Then into the treble

After the bass, the tuning moves into the treble (or vice versa, depending on habits). Same principle: progression by octaves, cross-checking intervals, and tuning each unison.In the extreme treble, beats are harder to perceive. Once again, sensation prevails. Personally, I prefer the high notes slightly sharp, adding brilliance and sparkle to the instrument.

The final pass: technique and musicality

A good tuning should be both technically correct and musically convincing. Throughout the process, it’s important to play chords, arpeggios, and listen to how the notes interact.At the end, each note is rechecked: sometimes a unison has drifted slightly, or a string has relaxed. A few touch-ups are made, then I’ll play a short piece or two.Finally, I invite the pianist to try the instrument—and I never leave until they are completely happy with the result.

In short

Tuning a piano isn’t just about turning pins. It’s about adjusting over 200 strings across nearly 8 octaves, following a precise acoustic logic, while adapting to the instrument, the room, and the pianist.

👉 If you’d like to see how it’s done in person, feel free to contact me. I’d be happy to show you how a piano that’s out of tune can, in about an hour, sound perfectly in tune again!