tone and terminology
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Hampshire Guitar Orchestra » Guitar stuff » hints & tips » tone production » tone and terminology
Tone and Terminology
A string vibrates at a rate we call its frequency. For example, the open A string vibrates 110 times a second - 110Hz.
But in addition to this fundamental, the vibration contains a mix of the individual harmonics or overtones that we can find over the 12th, 7th, 5th (and more) frets. For a string vibrating at 100Hz, the harmonics are 200, 300, 400... Hz.
Because of the logarithmic way that frequencies work, the harmonic sequence is a set of consonant tones, each higher than the previous by an octave, then a fifth, a fourth, a third... becoming ever closer, like the notes on a bugle.
We can't hear the harmonics, but their total blend is what makes a guitar
- strident & metallic (many harmonics)
- mellow & sweet (few harmonics)
One way to change the harmonic content
- Plucking near the bridge (sul ponti) gives the string an angular, asymmetrical shape when it is released - this promotes lots of harmonics
- Plucking halfway along (sul tasto) gives the string a gentle shape when it is released and this produces a smaller harmonic content
- Plucking right in the centre supresses all the even harmonics, making the sound "hollow" as well as sweet, like a clarinet
Another way to change the harmonic content is to change how the string is plucked - more later!
A picture's worth a thousand words
Here's a graphical representation (exaggerated for clarity) showing the fundamental & overtones for both a mellow and metallic sound.
The graphs show volume (upwards) against pitch (to the right)
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| Metallic sound | Mellow sound |
Unlike orchestral instruments, a guitar is not a sustaining instrument - every note dies away. The higher harmonics tend to die away faster, but it's a well-known phenomenon that it's the start of a note - the "transient" - that defines the character of the note. A note with high harmonic content can seem more "punchy" - a stronger start and (apparently) a faster decay, as the harmonics die away. A rounded sound has a less imposing start but can seem more sustained, as it does not evolve much as it decays.
So far...
So far, we've seen that...
- a mellow sound seems more sustained
Coming up...
Let's see how an understanding of the harmonic content of every note that we play can impact on our overall sound. Next page...