Pentatonic/Diatonic Relationships

When you think of pentatonic scales do you connect them to the diatonic key? Do you think of a major pentatonic scales as being rooted in the tonic of the key? 

For instance — most of us might believe the following; C major pentatonic 'belongs' to the key of C major ... G major pentatonic 'belongs' to the key of G major ... etc ... So that each major pentatonic scale is matched to a single major key. And of course, the relative minor pentatonic is matched to the relative minor of each key, so A minor pentatonic 'belongs' to the key of A minor, and so on.

You may also understand that when playing blues based music you can use an A minor pentatonic scale to riff on an A dominant7 chord, and also use an A major pentatonic with that same chord, and that doing so falls outside standard diatonic theory. 

But what about fully exploring diatonic possibilities of the pentatonic scale? Are you aware that each diatonic key contains not one, but three pentatonic scales, each with the same interval structure?

The key of C includes not only the C major/A minor pentatonic scales, but also G major/E minor and F major/D minor. 

Here are the notes of the key of C: C D E F G A B C ... 

... and here are the notes of the C major pentatonic scale: C D E G A C. 

Now, here are the notes of the G major pentatonic scale: G A B D E G, and the F major pentatonic scale: F G A C D G.

Notice that G maj. pent. and F maj. pent. contain no sharps or flats. So not only is each pentatonic scale rooted in the tonic of its own key, but it is also positioned within two additional keys. To be more precise, the I, IV and V degrees of any major key will produce a pentatonic scale with the intervals Wholestep, Wholestep, Minor 3rd, Wholestep,  Minor 3rd. 

Below you see the notes of each scale in the key of C as they appear on the fret board. The first is C major pentatonic, followed by F major pentatonic and then G major pentatonic:

(Zone names are based on the degrees of the diatonic major scale.)

And the interval structure of each scale:

We'll look deeper into the applications of this in the next post.

Symmetrical Root Position Triads

Triads are simple chords consisting of three tones. In the most fundamental form, the Root Position, the lowest pitched tone in a triad is the root. Chords are named for the root tone. The next tone in the chord is the 3rd, which is two steps above the root. The highest pitched tone in a root position triad is the 5th, which is two steps above the 3rd.

Every major key contains a set of seven triads, one rooted in each tone of the key. Because of the sequence of whole-steps and half-steps which comprise a key, three of the triads are major, three of the triads are minor, and one triad is diminished. The structure of these three triad forms is as follows;

Major Triad

Root [ major 3rd ] 3rd [ minor 3rd ] 5th

C - - - - - - - - - - - - E - - - - - - - - - - - - G

Minor Triad

Root [ minor 3rd ] 3rd [ major 3rd ] 5th

D - - - - - - - - - - - - F - - - - - - - - - - - - A

Diminished Triad

Root [ minor 3rd ] 3rd [ minor 3rd ] 5th

B - - - - - - - - - - - - D - - - - - - - - - - - - F

The sequence of major, minor and diminished chords in each key is as follows;

I - - - - ii - - - - iii - - - - IV - - - - V - - - - vi - - - - vii - - - - I

major -- minor -- minor -- major -- major -- minor -- dimin -- major

The diagram at the top of this entry shows the triads of the keys of C, D and E on the four top strings in their symmetrical positions around the Aeolian Axis and the Void Axis.


All contents of this blog are © Mark Newstetter