Every note created by a string (as discussed in the last music theory lesson) not only has the note you hear, it also has harmonic overtones.
These natural overtones of a note are the 3rd and 5th of that original note.
This means that, should you have three strings playing:
- First string play the root
- Second string 5/4 in length, playing the 3rd
- A third string at 2/3 in length, playing a 5th
Then these notes share the same overtones and when played at the same time, a most pleasant harmonic sound appear: a major triad.
The Major and Minor clash
Should you change the third to a minor third, or 6/5 rather than 5/4 in length you would get a minor chord, however, the major 3rd is still present in the overtones of the Root.
This means that you get a clash between the natural overtone of the Root (a major third) and the minor third.
This clash makes us experience the interval as “sad”, whereas when the 3rd was major, and it’s overtones perfectly repeated, we heard a “happy sound”.
The 3rd is as common in major and minor through out the chords we form when harmonizing a scale (more on this later).
Using the formula of repeating the natural overtones and then building new triads off those notes, we wouldn’t actually form a major scale, instead we have these notes created from that first major chord, and from now on I’m gonna use the note C a my starting point:
C Major Triad: C – E – G
E Major triad: E – G# – B
G Major Triad: G – B – D
Add them all up and we get this peculiar scale:
C D E ? G G#/Ab B
So there is no 4th and the A is flattened if we compare it with the standard major scale:
C D E F G A B
Two debates grew out of this:
Should the missing F be F or F#?
There’s a tone and a half gap between Ab and B, all other intervals are either a tone or a semitone away from each other.
So in ancient Greek times they simply raised the Ab to an A and decided to use an F#.
This gave us this basic scale:
C D E F# G A B, what we today call Lydian, a major scale with a #4.
Lydian as home
Lydian, to the Greeks was like major (Ionian) is to us today, it was seen as the home scale from which everything else was built.
This actually made complete sense since if you build all modes from this, the Lydian scale would feel the brightest, being the only scale with a # interval in relation to Root.
Putting Lydian first, we could describe the modes as going from sounding bright to sounding dark:
- Lydian, one sharp, the #4
- Ionian, no sharps or flats
- Mixolydian, one flat, the b7
- Dorian, two flats, b7 and m3
- Aeolian, three flats, b7, m3, b6
- Phrygian, four flats, b7, m3, b6, b2
- Locrian, five flats, b7, m3, b6, b2, b5
However, after a few more thousand years of debate, a switch was made and music composed in Ionian as our home was what we all accepted as sounding most natural, at least in the west!
Sheet music has since this change been based around the underlying rule of the major scale in C major being our home.
For the modern guitar player this evolution of scales and sheet music means:
Without understanding that it is the Ionian mode that sheet music is built around it would be impossible to read and write music on the stave.
Without being able to play the Ionian mode in all positions on the guitar neck it would be impossible to read music.
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