Warning: If you aren’t interested in the theory and technical side behind harmonics, you might want to skip this article because it will dive a little into the mathematics of how harmonics work. This is a discussion solely about harmonics, not just guitar harmonics.

There are a great variety of oscillators, such as a bowed violin string, a guitar string being plucked, and the human voice. These are all periodic, and therefore composed of harmonics.

The majority of passive oscillators will naturally oscillate at not only one, but at several different frequencies which are known as partials. Passive oscillators include such things as guitar strings, and a struck bell or drum head. It simply means they remain static objects unless initiated somehow by an outside force.

If the oscillator is long and thin, such as the column of air from a flute, or the string of a guitar then many of the partials will be integer multiples of the fundamental frequency. The sounds emitted by long, thin oscillators are generally going to be arranged harmonically. These are what we call harmonics and they are generally regarded as being musically pleasing.

On the other hand, partials with frequencies that are not integer multiples of the fundamental are called inharmonic. Instruments such as the piano or the cymbals create inharmonic sounds. Untrained human ears typically aren’t able to perceive harmonics as separate notes. This musical note that consists of many harmonically related frequencies is simply perceived to be one sound, with the quality of the sounds being a result of the relative strength of each individual harmonic frequency.

Guitar Harmonics | The Fundamental Frequency

Alright, on to some more fun stuff. A harmonic of a wave is a component frequency of a certain signal that is an integer multiple of the fundamental frequency. Basically, if you take the fundamental frequency and call it ff, then the harmonics would have frequencies of 2ff, 3ff, 4ff, 5ff etc. I think you get the general idea.

The interesting thing is that the harmonics have the property they they are all periodic at the fundamental frequency, meaning the sum of harmonics is periodic at that frequency as well. Harmonic frequencies will be equally spaced by the width of the fundamental frequency. They can be found by continually adding that frequency.

Here’s an example, if the fundamental frequency were to be 50 Hz, then the frequencies of the harmonics would be: 100 Hz, 150 Hz, 200 Hz and so on.

Guitar Harmonics | Crash Course

Now that we have all that out of the way with, there are just a few more things I would like to share about harmonics. When it comes to counting, harmonics aren’t overtones. This might be a little confusing at first but it will make sense as you progress in your understanding of music. Even numbered harmonics are going to be odd numbered overtones and the reverse is true as well.

Stringed instruments are also capable of producing some very pure sounding notes called harmonics, but knows as flageolets by many string players. These have a somewhat eerie quality to them in addition to being high in pitch.

Lastly, harmonics can be used to check at a unison the tuning of the strings that may not be tuned to the unison. For instance, you could lightly finger the node located half way down the highest string of a cello and tune it with the sound you get when lightly fingering the node located 1/3 of the way down on the second highest string. They both produce the same pitch.

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