A tuning curve made for one piano — right in your browser.
It listens to each string through your mic, reads the inharmonicity of that exact instrument (how strings drift slightly from whole-number partials), and draws a stretch curve for it. Seven temperaments, partial-by-partial octave matching, pitch-raise overpull, beat checks, and an 88-key tuning-order guide. No install, no audio upload.
Runs in the browser on desktop, tablet and phone. Open the same pianos on every device.
What a dedicated hardware tuner does — in a browser.
KUON PIANO is an electronic tuning device (ETD) for tuners. Where an ordinary tuner shows one target pitch, an ETD builds the optimal stretch curve for each individual piano and assigns a target frequency to all 88 keys. All you need is a microphone — no special hardware, no file upload.
A world-class core, piece by piece.
Measured-inharmonicity stretch
It captures each note’s partials through the mic and estimates the string inharmonicity coefficient B by least squares. Measure a few notes in the bass, middle and treble, and the curve for that one piano emerges.
Partial targeting
Choose whether each octave is matched on the 2:1, 4:2 or 6:3 partials, per register. Real partials are aligned beatless — a fuller bass, a singing treble.
Seven temperaments
Equal temperament plus historical tunings such as Vallotti, Kirnberger III, Young and meantone. Each is built from how its fifths are tempered and is verified to close the circle (the twelve fifth-deviations sum correctly).
Pitch raise / overpull
When bringing a badly flat piano up to pitch, it predicts how much each region will fall back as tension changes and shows an overpull target — so the rough pass is fast and lands true.
Beat checks
For test intervals such as thirds, fourths and fifths, it shows the theoretical beat rate per second — so you can cross-check by ear that the curve is being realised correctly.
88-key order guide & progress
From the temperament octave (F3–E4) outward. Hold the needle on zero and the key is marked done and advances automatically. See progress across all 88 keys at a glance.
Per-piano curves, synced
Register each customer’s piano by name and store its measured curve, A4 and temperament. Recall it with one tap next time. With cloud sync, open the same pianos from any device.
Reference A4, your choice
From 415 Hz early-music pitch to 442/443 Hz orchestral pitch. Presets and free entry are both supported, and the whole curve recomputes around your reference.
How to use it — five steps.
Even your first piano, start to finish without guessing.
- 1
Start the mic
Press “Start mic” and allow access. For accuracy the mic is captured with echo cancellation, noise suppression and auto-gain all turned off.
- 2
Choose the piano
Register the customer’s piano by name and set reference A4, temperament and stretch style (clean to wide). Next time, just pick it and the settings return.
- 3
Measure the curve (optional)
Capture a few notes in the bass, middle and treble with “Measure this note” to switch from the default curve to a curve measured for that exact piano. You can also proceed on the general default without measuring.
- 4
Tune along the guide
Turn on the guide and start at F3–E4. The key follows the note you play; hold the needle at zero and it is marked done and moves on. After the temperament octave, work outward.
- 5
Pitch-raise if needed
If the whole piano sits well below pitch, turn on “Pitch raise”. It shows an overpull target; tune until the needle reads zero to finish the rough pass, then turn it off for the fine pass.
Your sound never leaves your browser.
All microphone analysis runs on your device; recordings and audio are never sent to a server. What gets stored is only the piano’s name, its measured curve and settings — synced so you can use them across devices.
Frequently asked
Do I need to install anything?
No. Just open it in a browser — any OS, any device.
Does it work for grands and uprights?
Yes. Because the curve is built from measured inharmonicity, it adapts to either instrument. Measure it and the curve becomes specific to that piano.
Can I choose temperaments?
Yes — equal temperament plus historical tunings like Vallotti, Kirnberger III, Young and meantone. You can also lower A4 to 415 Hz and similar for early music.
Does it handle pitch raises?
Yes. It shows an overpull target that anticipates how much each region falls back as tension changes — a fast rough pass, then a fine pass to finish.
Can I measure offline?
The core of measuring and tuning runs in the browser. A connection is used when syncing saved pianos across devices, but the tuning work in front of you proceeds reliably.
Is a phone’s built-in mic enough?
In most settings it captures partials well enough. A quiet room and placing it near the strings help. Measuring a few notes per register makes the curve more stable.
For every player other than piano — voice, strings, winds, guitar — there is KUON TUNER, the unified tuner and pitch coach.
KUON TUNER →Draw the curve for that one piano now.
Open it in a browser and allow the mic — that’s all.
Open the app