The other day, the piano tuner came to the semi-annual tuning of my piano (a Blüthner baby grand). I was not at the house when he did the tuning. When I got home, the piano was tuned in respect to itself but not according to the absolute pitch (about 15 cent down). I used the "Cleartune" Iphone app to determine that. This piano tuner has been tuning my piano for three years and is very professional.

Is this considered a tuning mistake? Is an absolute difference of 15 cent is even distinguishable by a human ear?

  • You have used the same piano tuner for three years, kept the piano regularly tuned, and this is the first time it has been tuned lower? Or is this the first time you have checked it against an external source? Apr 16, 2012 at 22:42
  • @200_success I checked the two visit before the last visit , and this is the first time it was tuned lower.
    – iddober
    Apr 17, 2012 at 7:05
  • I can understand tuning it low if it was already flat, so as not to put too much stress on the frame all at once. However, if it was already close to standard pitch, that's just bizarre. I would ask your tuner to stop by to check it whenever he happens to be in the neighborhood. Apr 17, 2012 at 14:55
  • 2
    Which keys did you measure? Did you take stretched tuning into account?
    – endolith
    Jul 7, 2012 at 16:53

8 Answers 8


It's pretty common place to tune a piano lower as it gets older since that puts less mechanical force on the frame. However that should better be done by consulting the owner and then bite the bullet and tune it down a full half step (so you can still play with others by transposing).

15 cent close to the "just noticeable difference" or jnd but it can certainly be audible. This website has some audible example of a middle C at different rates of detune.

It's also possible that your iPhone's internal crystal is slightly out of whack. In order to build a good tuner you need a reasonably good reference clock and the IPhone hardware has no particular reason to have one with a tightly controlled center frequency.

  • 4
    Good thinking about the crystal precision, but 15 cents off is too large for that. 15 cents at the 440 Hz A is an offset of around 4 Hz, that is 0.1 %. A crystal in the iPhone should be at worst +/- 20 parts per million (ppm), 0.1 % would be outrageous. That said, I wouldn't trust the writers of the app to give that level of precision, even if the hardware should.
    – Gauthier
    Apr 13, 2012 at 18:11
  • 1
    Playing with others isn't really an issue unless their tuning holds well, and it takes more than a few minutes to re-tune. Other than melodic percussion and recordings, there wouldn't be many instruments inside a house that would pose a problem. Guitar, string, and wind instruments all have to be tuned each time they're played (or in the case of wind instruments, when they're played with others) anyway, so having the piano 15 cent out isn't that big a deal. Still, bring it up with your piano tuner.
    – MBraedley
    Apr 13, 2012 at 23:14
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    @Gauthier: I wasn't implying that the clock drift itself is out of spec, but that at some point Apple switched vendors or parts with a slightly different nominal frequency (say for the CPU clock). They have no reason not to.
    – Hilmar
    Apr 14, 2012 at 15:48

From the perspective of a piano tuner, 15cts is a huge descrepency. It must have been tuned that way on purpose. Probably because a piano that low would require a pitch raise (and thus an additional charge) to bring up to concert pitch. Since you weren't there, he/she probably decided to leave it where it was. I would always talk to the owner before leaving a piano anywhere but right at concert pitch.


I highly recommend you do the following.

1) get a calibrated tuning fork and test one more time that your A 440 is off. So you are absolutely sure.

2) have a friendly chat with your tuner to discuss why this is off.

No one here can read minds. You really need to talk to your tuner about why he/she did not tune it the way you expected.

I also recommend that you are around the next time the tuner comes as this is a good time to discuss the condition and care of your piano. Have him check the action and check the hammers up close. My tuner removed the action last time and showed me what is breaking down. Although my studio grand is reaching 100 years old, it can still be tuned to concert pitch. I suppose because this was a quality build that it is aging well (Steinway).

  • 2
    "Is this considered a tuning mistake? Is an absolute difference of 15 cent is even distinguishable by a human ear?" <--- That is the question. What does reading the OPs mind have to do with this? Apr 13, 2012 at 19:24
  • 4
    Mind reading refers to the piano tuner as no one here knows what he was thinking, what he perceived and why he made his choices.
    – filzilla
    Apr 13, 2012 at 19:34

Did you measure at A above middle-C? (A4) The Cleartune app may not take the inharmonicity of your piano into account. Depending on how far away from that reference it is measured, you may see confusing results.

When I installed the professional tuning software called Tunelab on my iPhone and iPod Touch, it did not need calibration at all on either device when compared to the NIST analog standard. Spot-on, to the accuracy allowed by the calibration function of the software. I do not know if this is typical, but I suspect there is not that much variation between devices, at least not enough to be off by 15-cents at A4 (about 4 Hz).

Was there direct sunlight on the piano when you measured it? A tuner should call out environmental conditions that may affect your tuning stability. Temperature change is one way to get very rapid instability on your tuning.

A possible reason for "floating" pitch, since you say it is tuned twice a year, is if your piano has a relatively wide natural variation in pitch from low to high humidity seasons. Depending on the particular time of year, a tuner may not watch to "chase" the pitch up and down with the seasons. In this situation, I would try to recommend the best time of year to tune such that a piano would be close to pitch for as long as possible.

There are many variables, I would definitely ask your tuner what his intent was, describe how you took the measurements, and see what his response is.


jbm had some great points. As did a few others. I see that this post is an old one, but the question does come up frequently. So here's my 2 cents (no pun intended). First, nice piano.  Second, always talk to your tuner immediately upon discovering any topic of concern.  The sooner, the better.  Then my recommendation is to get a temperature and humidity gauge that records minimum and maximum levels for both.  Then place it on the piano and observe the results over the following days, weeks, months and seasons.  The more stable the temperature and humidity in and around the piano, the more stable the tuning will be and the better for the piano over all.  


A quick qualifier about myself.  I am the 5th generation in a 6 generation piano business.  I have personally rebuilt, restored, repaired, or tuned hundreds of pianos and have been responsible for thousands more.  I have been using a computer controlled tuning instrument for over 25 years.  It creates a custom stretch tuning for each piano, taking into consideration that pianos unique inharmonicity.  So I feel that I know something about computer aided piano tuning.


Back to your question.  One (1) Hertz (aka cycles per second) equals 4 cents.  Concert pitch of A-440 is simply means three strings at A4 vibrating in unison at 440 cycles per second - period.  Doesn't matter if it's summer or winter; an aural (by ear) tuning or a computer aided tuning ... A-440 is A-440.


One hundred (100) cents constitutes a semitone, also known as a half-tone or half-step.  Therefore, A4 to A#4 is a semitone or 100 cents (¢).  In your example of 15¢ flat (15/4= 3.75 Hertz flat) your piano was at A-436.25 (when you measured it) or 0.852273% flat. If you live in the northeast, seasonal changes will produce greater changes in pitch than that.  You would be doing a pitch raising in the winter and pitch lowering in the summer; changing the pressure within the piano by thousands of pounds each time.  To put it into perspective, a concert piano is tuned before every concert. We include 4 tunings and an action regulation check during the first year.  We install a humidifying/dehumidfing system with a humidistatic control when we are commissioned to do a restoration or rebuild - that is how important humidity control and maintenance is to us and the piano.  If your piano is near a window, door, fireplace, air conditioner, etc. you will have frequent pitch changes making getting a solid, long-lasting, right on pitch tuning next to impossible.


Regarding informing the customer of the pianos condition.  Before we even book a tuning for a new customer, we ask several questions.  Such as: is the piano played with other instruments (or voice)?  What is your piano playing skill level?  Does any one else ever play it?  When was it last tuned?  How old is the piano?  Plus many others.  The point is, we try to gauge.their needs and expectations and discuss them BEFORE we even book the tuning.  Discussing a pianos condition too much while at the house usually doesn't turn-out very well.  Just telling someone that a piano should be tuned 4 times the first year (if new), twice a year thereafter and the action regulated every 5 years can be a big turn-off.  When was the last time someone checked your plate screws for tightness, set the strings on the bridges, spaced the strings, filed & voiced the hammers?  How often have you heard that you should tune a piano at least once-a-year?  Especially if it's not being used!  Once-a-year tuning is an insurance policy to protect your investment and minimize long-term damage to the piano.  If three piano is not worth tuning one a year, sell it.  I can not remember how many pianos have be ruined by lack of service.  I can remember the few that were destroyed by abuse.  I hope that this is helpful to future readers of your post.


Not sure if this was mentioned, but some piano tuners like to "float" the pitch.

Floating the pitch means tuning A4 slightly flat in the winter and slightly sharp in the summer.

The rational is that if you tune a piano in the summer, it will eventual go flat in the winer, so if you tune it sharp, then it will settle close to A440 as the humidity drops. Similar reasoning for tuning flat in the winter.

Also, there is less pitch change to make if you come to a sharp piano in the summer and don't bring it all the way down to A440.

I never do this because I use a technique that creates extremely high accuracy octaves that are also precise, meaning I can repeat their size all the way up the piano.

Floating the pitch for me means I have to retune the treble and bass every time. When I tune A4 at A440, I will often get to the extremes and they will not need to be changed. The extra work to move A4 to 440 is saved in the extremes.

If your piano was tuned in the winter, it very well may have been floated. Ask your technician.

  • Roughly how many cents would the variation per season be? I got a (relatively cheap) piano new that only had one tuning in 3 years, and only now bothered to measure where it's at. A few unison strings obviously out, but the whole thing is uniformly about 7c flat (measured by 2 tuners). Given that I live near WashingtonDC and it is winter, maybe that's where it should be? This was a starter upright when I wasn't sure of my child's commitment. I may actually get a good one and use the existing one to learn self-tuning on.
    – Rob
    Feb 22, 2015 at 3:52

The Bluthner base strings are a bit prone to snapping if over-pulled, and it might be the case your tuner was afraid to put any more strain on them and so perhaps he decided impromptu to leave the whole piano flat. Just a thought.


Good answers. Just some clarifications. 1hz at 440 is about 4 cents. Someone mentioned 15 cents. A tuning fork can vary up to 3 cents easily just from moderate temperature differences. Swings due to season changes, in my professional experience (tuning for 16 years) can be up to about 4hz. That's 16 cents at A4. Calibration of tuning software accounts for the variation in clock speed of different computers but in no way comes close to 15 cents. I've used NIST to calibrate Tunelab as part of teaching my tuning courses and it is a very small fine adjustment if any, far less than 1 cent. Call your tuner.

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