C Nature's Scale
The next logical progression in our journey to understand understand the underlying theory of microtonal guitars is creating a tuning system. A tuning system is the way you notes or pitches on the instruments that you are playing are constructed. First we will create a tuning system using the 5 limit major scale for the 1, 4, and 5 chords to create the ratio's for all the intervals we will need. Let's look at the 5 limit diatonic major scale below:
F Nature's Scale - C Nature's Scale Ratio's
Next let's take this same scale and build it for the key of F, the 4th scale degree of the diatonic scale in the key of c. Since our objective is to create a "combined" scale of these respective diatonic scales we need to multiply the ratio that is the root of the new scale by the ratio we want to generate for the scale, the result is the ratio in relation to the root of the parent scale (in this case the key of c).
G Nature's Scale - C Major Ratio's
Now let's do calculate the ratio's for the major diatonic scale for G and the ratio's in relationship to the root.
C Combined Nature's Scale with F & G Major
Let's finish up this scale by adding the notes that aren't present in C Major from the F and G major diatonic scales, like we did in lesson 2, to create a "combined major scale". Notice this is an 11 note scale and isn't a full chromatic scale. This scale doesn't have any note/ratio's for a minor 2nd, minor 3rd or minor 6th. Also note how there are 2 different major seconds, 10/9 and 9/8, we will come back to this in feature writings.
C Combined Nature's Scale with Fretboard
Below is a diagram of how these intervals are mapped out on a guitar fretboard tuned to Open D tuning using the above intervals as a map for the neck.