String Theory

Friday, May 30 2008 @ 09:25 AM UTC

OK, I'm not writing an article on the hypothetical theory trying to unite quantum mechanics and general relativity.

What I am going to try and explain to you, and for my own benefit, is how the length of a string is related to the note it produces when plucked, as well as the importance of it's harmonic overtones

• A string of a particular length and a particular tension will vibrate at a particular frequency. This is the frequency of the note produced
• Dividing the length of this string exactly in half will halve the wavelength. This means that it also doubles the frequency.
• Doubling the frequency (or halving the wavelength) will give you the same note one octave up
• This string will also produce a number of "overtones", that can be isolated by playing the harmonics
• The harmonics are located at particular points of the string: 1/2, 1/3, 1/4, 1/5 etc... of the way up. Check out this really useful reference poster and article from wikipedia: Table of Harmonics - Harmonic Series
• The strongest harmonics are at 1/2, 1/3 and 1/4 up the string. These are on the 12th fret (double dot on a guitar), 7th Fret and 5th fret respectively
• These harmonics produce notes one octave up, and octave plus a perfect fifth, and then two octaves up from the fundamental note of the open string
• Fretting these positions give you one octave up, a perfect fifth and a perfect fourth
• Playing the chords on these frets that are appropriate for the key in question (i.e. the major key of the fundamental note of the open string) will give you the three most popular chords in music. So if we're looking at the E string of a guitar, this will generate an Emajor, an Amajor and a Bmajor. For the A string, it will give you A, D and E.

Anyway, enough rabbiting on for now. I'll write some more when I get the time / inspiration.

Keep practicing.

http://www.theguitarmaster.co.uk/article.php/string-theory