Tuning Your Own Piano: Touching Up a Single Note

A note that sounds “sour” or a unison that has drifted can sometimes be fixed yourself, with care. This tuner helps you measure and check; a full tuning remains the job of a professional piano technician.

The microphone is only requested when you tap the button. Sound is analysed on your device; nothing is recorded. Open the full app

What you can reasonably do yourself

Tuning a whole piano takes hours, skills built up over several years and a good understanding of the instrument’s mechanics. Pulling on more than 200 strings changes the tension across the entire structure: a clumsy correction in one place throws others off.

On the other hand, sometimes a single note stands out: one of the two or three strings of a unison has moved and the note sounds “out of tune”, with a chorus-like effect. That is the typical case where a careful touch-up is possible. If several notes are off, if the whole piano is flat, or if it has not been tuned in years, call a professional: raising the pitch of a piano is a risky operation.

Reference table

Deviation from equal temperament, in cents (C = 0)
Temperament	C♯	D	E♭	E	F	F♯	G	G♯	A	B♭	B
Equal	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Pythagorean	+13.7	+3.9	−5.9	+7.8	−2.0	+11.7	+2.0	+15.6	+5.9	−3.9	+9.8
Werckmeister III	−9.8	−7.8	−5.9	−9.8	−2.0	−11.7	−3.9	−7.8	−11.7	−3.9	−7.8
Vallotti	−5.9	−3.9	−2.0	−7.8	+2.0	−7.8	−2.0	−3.9	−5.9	0.0	−9.8
Quarter-comma meantone	−24.0	−6.8	+10.3	−13.7	+3.4	−20.5	−3.4	−27.4	−10.3	+6.8	−17.1
Kirnberger III	−9.8	−6.8	−5.9	−13.7	−2.0	−9.8	−3.4	−7.8	−10.3	−3.9	−11.7
Kellner	−9.8	−5.5	−5.9	−10.9	−2.0	−11.7	−2.7	−7.8	−8.2	−3.9	−9.0
Young II	−9.8	−3.9	−5.9	−7.8	−2.0	−11.7	−2.0	−7.8	−5.9	−3.9	−9.8
Neidhardt “large city” (1724)	−3.9	−3.9	−2.0	−5.9	−2.0	−3.9	−2.0	−3.9	−5.9	−2.0	−3.9
Just intonation (Zarlino)	+11.7	+3.9	+15.6	−13.7	−2.0	−9.8	+2.0	+13.7	−15.6	+17.6	−11.7

Touching up a unison, step by step

Find the note on the 88-key keyboard shown on screen, from A0 to C8, or let automatic detection identify it.
Isolate the strings: slip in a rubber mute or a felt strip so that only one string rings.
Measure each string separately and spot the one that differs from the others.
Remove the mute from one in-tune string and from the out-of-tune string, play both together and start the beat measurement.
With the tuning lever, move the pin of the out-of-tune string very slightly until the beats slow down and then disappear.
Remove the mutes, play the note firmly several times and check that it stays stable.

Beats: the piano tuner’s tool

Two strings at almost the same pitch produce a pulsation whose rate equals their difference in hertz. On A4 at 440 Hz, a string at 441 Hz produces one beat per second, a gap of only about 3.9 cents.

In the middle register, a clean unison should hardly beat at all. The app measures beats per second while both strings are sounding: this is more reliable than a reading in cents for setting a unison, because what matters is how the strings agree with each other.

Stretch tuning and the Railsback curve

A well-tuned piano is not tuned exactly to theoretical equal temperament. Because the strings are stiff, their harmonics sound slightly higher than whole-number multiples of the fundamental: this is inharmonicity. To make octaves sound in tune, the tuner “stretches” the tuning, lowering the bass slightly and raising the treble. The resulting curve is known as the Railsback curve.

The app offers a typical stretch curve depending on the piano type: upright, baby grand or concert grand. It is only a guide: each instrument has its own inharmonicity, generally stronger on small pianos with short strings.

To go further, the app can measure a note’s inharmonicity coefficient B and calculate a stretch from two notes measured on your piano. For a unison touch-up this is not necessary: simply bring the out-of-tune string in line with the in-tune strings of the same note.

Dealing with bass notes

In the bass, the fundamental is weak and the harmonics dominate. The tuner may then pick the wrong octave or hesitate. Partial tuning solves this: the app locks onto the 2nd or 4th partial, which is clearer, and works out the pitch of the note from it.

The wound bass strings are also the slowest to have remade and the most expensive to replace: be extra careful.

Safety and precautions

Use a proper tuning lever of the right size: pliers or an ill-fitting wrench will damage the tuning pins.
Make tiny movements: a few degrees of rotation are enough to change the pitch noticeably.
Never pull a string far above its pitch: an old or rusty string can break and whip. Keep your face at a distance.
Remove all mutes and tools before closing the piano.
If the pin turns with no resistance or will not hold, stop: the pinblock may be worn, and that calls for a repair.
When in doubt, contact a piano technician: a broken string or a damaged pin costs far more than a tuning.

Keeping a record

The tuning log records the measured deviation of every note you test. It lets you check the overall condition of the piano before calling a technician, or follow how well the tuning holds through the seasons. The historical temperaments shown in the temperaments table are mostly of interest to harpsichordists and the curious: a modern piano is tuned in equal temperament.

Frequently asked questions

Can you tune a piano yourself with an app?

A one-off touch-up, such as an out-of-tune unison, is possible with the right tuning lever and a lot of care. A full tuning requires training and remains a job for a professional.

What is the frequency of the lowest note on a piano?

A0, the first key of an 88-key piano, vibrates at 27.50 Hz. The highest note, C8, is at 4,186.01 Hz.

Why does my tuner say the top notes of my piano are too sharp?

A well-tuned piano is stretched: its treble is deliberately a little above theoretical equal temperament. Turn on the stretch curve to compare against a more realistic target.

What is a unison on a piano?

In the middle and upper registers, each note strikes two or three strings tuned together. If one of them moves, the note sounds cloudy, and that unison is what needs touching up.

Why does the tuner hesitate on bass notes?

The fundamental of bass notes is weak compared with their harmonics. Use partial tuning, on the 2nd or 4th partial, for a stable reading.

What is the inharmonicity coefficient B?

It measures how far a string’s harmonics deviate from whole-number multiples of the fundamental. The larger it is, the more the tuning needs to be stretched.

My whole piano is flat, can I bring it back up to pitch?

Doing it yourself is not recommended. Raising a whole piano greatly increases the tension on the frame and strings; a professional does it in several passes.