Many people wonder if they can simply tune their pianos with a guitar tuner. It’s a question I’ve asked myself, before I became a piano technician. The first tuning I ever did was on a little Schumann grand piano with a guitar tuning app.
The short answer is yes; but it’s highly inadvisable. It will sound awful to anyone with a decent ear, and downright unacceptable to piano players. There are subjective elements to tuning instruments, and an “accurate” tuning is a slightly shifting scale. A good tuning on any given instrument, including pianos, will take into account the design of the instrument and the mechanism it uses to produce sound. For example, a pipe organ is tuned differently than a piano because a pipe organ uses air forced through pipes, and a piano uses a felt hammer which is hurled at a tense wire.
The key difference between instruments from the perspective of tuning is something called inharmonicity. An instrument is inharmonic if the tones it produces don’t line up with the harmonic series, which is an important factor in deciding the best tuning. There are varying degrees of inharmonicity in instruments, and a piano has more inharmonicity than a guitar. This means that pianos are tuned differently than guitars, so something that is meant for tuning guitars won’t work well on pianos.
If you want to go down the rabbit hole of the harmonic series, inharmonicity, and how they affect tuning, the following will get you on your way.
The Harmonic Series
When a note is played on an instrument, your ear is actually hearing a stack of different frequencies at the same time. The range of frequencies contained in that note is known as the harmonic series. It is also referred to as the overtone series or the partial series, because, apparently, having one name for it isn’t complicated enough. For the purposes of this article I will refer to it as the harmonic series, and the specific frequencies within it as harmonics.
When the note C is played, for instance, what that note consists of is a stack of frequencies with C at the bottom. Ascending from that first C, the stack goes like this:
(graphic from: https://www.beyondmusictheory.org/the-harmonic-series/)
As you may have noticed, all the notes in a C major chord, and then some, are present. This natural phenomenon is deeply intertwined with the formation of music. The frequencies in the series are also mathematically related to each other. The 2nd harmonic is roughly twice the frequency in hertz of the 1st harmonic, and in musical terms is one octave up. So, if our sample note is C4, the 1st harmonic would be about 262hz and the 2nd harmonic would be about 524hz. The 3rd harmonic is the first G after the 2nd harmonic and the 4th harmonic is two octaves above the 1st harmonic, or about 1048hz.
Here it is represented on a keyboard:
(graphic from: https://scienceofmusicperformance.blogspot.com/2015/10/harmonic-overtone-series-lesson-plan.html)
The first 6 harmonics in the series are vital in determining the best tuning for a piano. When tuning a C5 on a piano, for instance, the tuner has to make sure that the 1st harmonic is tuned to the 2nd harmonic in the C4 below it in a way that is pleasing to the ear, and so on and so forth. This, as you will see, is not always straightforward. That’s where inharmonicity comes into play.
Inharmonicity refers to the fact that, depending on the mechanism with which the note is sounded, the harmonic series shifts slightly. To return to the example from before, the harmonic series from a C4 played on a pipe organ doesn’t exactly match the harmonic series from a C4 played on a piano. The values in hertz of the harmonic series on the pipe organ are identical to the values of a pure harmonic series, where every octave up is twice the value of the octave below it. The harmonic series on a piano, however, is stretched, meaning that in many cases the 2nd harmonic is more than twice the frequency of the 1st harmonic, and all the other harmonics usually have higher values as well. This is because hurling a felt hammer at a tense wire produces a more chaotic result than continuously forcing air through a pipe, or picking a string with a guitar pick.
Different instruments have different levels of inharmonicity inherent in their design. Bowed string instruments, brass instruments, and reed instruments are perfectly harmonic, meaning they match the purely mathematical harmonic series perfectly. Plucked instruments, such as guitars and harpsichords, are nearly harmonic. Pitched percussion instruments, which is the category that the piano falls into, are approximately harmonic. This means that pianos have more inharmonicity than guitars, which is why a guitar tuner won’t give you a good piano tuning. The harmonic series from a note played on a guitar is different than the harmonic series from a note played on a piano, and a good tuning needs to take that into account.
Aural Piano Tuning
When piano technicians tune a piano aurally, meaning by ear, they listen to how the harmonics in the notes they are tuning interact with each other. For the sake of simplicity, which is desperately needed when trying to wade into the seething waters of tuning theory, we will stick with the 1st harmonic and the 2nd harmonic. Just keep in mind that piano technicians and sophisticated piano tuning apps use multiple harmonics to determine the best way forward when tuning.
When tuning a C5 to a C4 on a piano, for example, the tuner has to take into account how the 1st harmonic of the C5 interacts with the 2nd harmonic of the C4. Since C5 is one octave above C4 and the 2nd harmonic of the C4 is one octave above its 1st harmonic, the frequencies of the 1st harmonic of C5 and the 2nd harmonic of C4 need to be in tune with one another. If they aren’t in tune they will produce a rapid wah-wah-wah sound that is unpleasant to the ear, which piano technicians call “beating.”
Since a piano has a high degree of inharmonicity, the frequency of the 2nd harmonic of the C4 will usually be more than twice frequency of the 1st harmonic. In musical terms it will be sharp compared to what it should be in a perfect harmonic series. This means that the C5 that is being tuned must also be sharp, or it will cause beating. If there is too much beating in the tuning of a piano it will sound muddy and inarticulate. Furthermore, that means that the C5 on a piano will most likely be tuned sharper than the C5 on a guitar, because that will help the piano sound more in tune with itself.
So, all things considered, a guitar tuner is a poor substitute for the tuning you would get from an experienced technician. A well-crafted piano tuning app will give you the measurements for a good tuning, which is a good start, but tuning a piano well also requires a certain skill set that can take years to cultivate.