Why Does My Piano Still Sound "Off" Right After It's Been Tuned?

Every so often, I'll finish a tuning and the piano owner will play a few notes, pause, and ask something like "are you sure that's right?" I’ve even had people “check” the piano with a digital tuner app from their phone and see that it doesn’t match up perfectly.

It's a completely fair question — and usually, the piano is exactly where it should be. What's actually happening comes down to two concepts that most piano owners have never heard of: stretch tuning and inharmonicity. Understanding them explains almost every version of "this doesn't sound quite in tune to me" that I hear.

It's Not Actually Out of Tune — It's Not Tuned the Way You'd Expect

If you tuned a piano using a simple, mathematically "perfect" frequency for every note — exactly double the frequency an octave up, exactly the ratios you'd get from a physics textbook — it would actually sound worse than a properly tuned piano, not better.

That's counterintuitive, but it comes down to how piano strings physically behave.

Inharmonicity: Why Piano Strings Don't Vibrate "Perfectly"

When a string vibrates, it doesn't just vibrate as one clean wave — it also vibrates in smaller segments at the same time, producing overtones (harmonics) above the main pitch.

In an idealized, perfectly flexible string, those overtones would land at exact whole-number multiples of the main pitch (if you’ve studied differential equations, you’ve probably even derived these frequencies from the “wave equation”).

But real piano strings are stiff, not perfectly flexible, and that stiffness causes the overtones to land slightly sharp of where pure math says they should be. This effect is called inharmonicity, and it's more pronounced in shorter, thicker strings (like the bass strings) than in longer, thinner ones.

Every piano has its own inharmonicity fingerprint based on its scale design, string length, and construction — which is part of why two different pianos, both "in tune," can still sound subtly different from each other.

It’s also part of why a concert grand piano sounds so much better than a small spinet, even after a perfect expert tuning. Small spinets have much more inharmonicity due to the short string lengths.

Stretch Tuning: Working With Inharmonicity Instead of Against It

Because of inharmonicity, a skilled tuner doesn't tune every octave to a mathematically pure 2:1 ratio. Instead, the tuning is "stretched" — bass notes are tuned slightly flatter and treble notes slightly sharper than pure math would suggest — so that the overtones line up in a way that minimizes the destructive interference of those waves (the “wah, wah, wah” sound) across the piano's range.

This is called stretch tuning, and it's not a shortcut or a compromise; it's the correct, intentional way to tune a piano so it sounds unified and pleasant to the human ear rather than technically "correct" but harsh.

This is also exactly why an electronic tuner or tuning app by itself isn't enough to properly tune a piano — a good tuning either requires an ear trained to hear these relationships, or software (like the ones professional techs use, which factor in each individual piano's own inharmonicity curve) that goes well beyond a basic pitch-matching app.

This means you’ll see that most notes do not perfectly line up with a digital tuner, and every piano will be off by a different amount.

So Why Does a Correctly Tuned Piano Sometimes Sound "Off" to You?

A few common reasons:

You're comparing it to an electronic tuner or another instrument. If you check a note against a basic chromatic tuner app, the treble and bass notes may appear "sharp" or "flat" relative to that app's pure mathematical reference — even though they're exactly where they should be for that piano, because of stretch tuning.

You're used to how it sounded when it was already out of tune. This happens more than people expect. If a piano has drifted gradually over a year or two, your ear slowly adjusts to the "new normal." When it's brought back to correct pitch, the correct sound can feel unfamiliar at first, simply because it's different from what you'd gotten used to.

A pitch raise was needed. If a piano had drifted significantly flat, a single pass often can't get it all the way to stable pitch — I do a two-pass tuning specifically to account for this, where the first pass gets it close and the second pass fine-tunes it. Right after a big pitch raise, a piano can be more unstable for the first days or weeks as the strings settle into their new tension, and very occasionally a note or two might need a small touch-up shortly after.

Something else changed. Room temperature, a nearby heating vent, or even just the piano being freshly played after a long silence can make a piano sound subtly different for a short adjustment period.

When It's Worth a Second Look

If something sounds genuinely off — not just unfamiliar, but a specific note that sounds noticeably wrong, a buzz, or a beating/wobbling sound between two notes played together — that's worth mentioning.

I stand behind my tunings, and if there's a real issue, I want to know about it rather than have you live with something that doesn't sound right.

What could be happening is something more severe, like a crack in the soundboard or rusty strings causing artificial beats that make a note, even when not played with any other note, to sound out of tune.

I service pianos throughout Chaplin, Willimantic, Coventry, Storrs, Windham, and the surrounding Windham and Tolland County area. If your piano doesn't sound the way you expected after a tuning — mine or anyone else's — feel free to book an appointment online or reach out and we can talk through what you're hearing.

And remember, I have a guarantee. If something is off within 30 days of an appointment, I will come back to diagnose the problem free of charge.