Harmonics are one of the most used extended techniques that the guitar has to offer, whether it be for classical, finger style or acoustic repertoire. But what are the physics behind harmonics on the guitar, and how can we use that knowledge to help us hit the right note every time?
The physics behind harmonics on the guitar
Each note that we hear is a mixture of many different pitches. Just like the retina turns the light that hits it into electric signals that our brain interprets into the objects, colours and textures, sound waves enter our ear, causing the eardrum to vibrate which sends signals to the brain which interprets these vibrations into sounds that we recognise and understand.
The three tiny bones in the middle ear (ossicles) form a chain from the ear drum to the inner ear, which interprets how fast the eardrum moves back and forth into what we understand in music as pitch. Each pitch is made up of a series of ‘clues’ which we use to define its identity, the overtone series.
Simply, the overtone series is made up of integer multiples of the ‘fundamental’ tone.
The overtone series of C3
The harmonic series of “E”
When we play a harmonic, we are essentially changing the length of the string and modifying how the string vibrates; when we play a harmonic at the 12th fret, we are splitting the string into halves, when we play a harmonic at the 7th or 19th fret we are splitting the string into thirds, etc.
Harmonic frequencies on the 6th string of the guitar
Two Types of Harmonics
On the guitar there are two ways of producing harmonics, natural and artificial. This article will explain exactly how to produce a clear and ringing tone from both of these types of harmonics.
In order to play a natural harmonic, we require precision from both the left hand and right hand simultaneously. The left hand finger must exert the exact amount of pressure to modify the division of the string, this means somewhere exactly between pressing the string down into the fretboard and not playing the string at all. Use the below example at your guitar to find this pressure point.
Hovering above the 12th fret with a left hand finger of your choice, repeatedly play the string over which you are hovering with the nail of the right hand thumb. You should at this point be hearing the open string played repeatedly and metallically. Once this movement is in motion with the right hand finger, steadily lower the left hand finger onto the string of your choice exactly over the metal of the 12th fret. Move as slowly as possible and with even precision of speed, as if your finger were a piece of machinery.
Observe the difference in sound and pitch of the string when your finger makes first contact with the string. It is somewhere in the flux between barely touching the string and pressing the string that you will hear the pitch jump an octave higher - this is the natural harmonic on the 12th fret.
Artificial harmonics are created by making two points of contact with the right hand, this technique is used to not only facilitate easier playing in certain passages, but to create more harmonics on the instrument, as when used in combination with string shortening with the left hand it is possible to create notes that otherwise would not be possible with only natural harmonics.
In order to create an artificial harmonic, the thumb and the pad of the index finger both make contact with the desired string, as in the below diagram taken from Mircea Gogoncea’s Tonebase class on Understanding and Playing Harmonics.
Considerations for sound
If your harmonics are not coming out cleanly or as bright as you wish, it is probably because of one of four reasons:
- You are releasing the string too early with the left hand - causing the string to buzz or be a sort of ‘half harmonic’.
- You are releasing the string too late with the left hand - causing the string to produce a harmonic that sounds muffled and dies very quickly.
- You are not placing the left hand finger in the right place - remember that the position for the harmonics is right over the metal of the fret, rather than somewhere just before it.
- You are not synchronising the right and left hand correctly, remember that just as when you play anything on the fretboard, precision is absolutely key, your best bet for a beautiful harmonic sound that rings out like a bell is to release the right hand and left hand fingers in perfect synchronicity - hint: when playing natural harmonics this means first the right hand finger, proceeded immediately by the release of the left hand finger.