Pitch Axis Theory
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Pitch axis theory is a musical technique used in constructing chord progressions. The tonic, or root, is used as the base note, and melodic scales are chosen according to the chords that lie beneath them.
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[edit] Concept
The seven modern modes are all connected to each other by diatonic shifts; that is, C Ionian (C-D-E-F-G-A-B-C) is also D Dorian (D-E-F-G-A-B-C-D), E Phrygian (E-F-G-A-B-C-D-E) and so on, until you return to the original C Ionian Mode. Therefore, each of the seven modes of any of the twelve major keys is also a mode for another six of the modes in that particular key.
Pitch axis theory suggests that for each mode, there is a chord that accompanies it. When that chord occurs, the corresponding mode should be used for the melody or for soloing.
The more common modes, along with their chords:
| Mode | Chord(s) |
|---|---|
| Ionian mode | Maj6, Maj7 |
| Dorian mode | Min6, Min7 |
| Phrygian mode | Min7, Min7b9 |
| Phrygian Dominant mode | 7, 7b9 |
| Lydian mode | Maj7, Maj7#11 |
| Mixolydian mode | Dom7, Dom9, Dom11 |
| Aeolian mode | Min7, Min9, Min11 |
| Locrian mode | Dim7, Dim7b9 |
This is the first part of pitch axis theory. The second step is implementing these modes as chords built on a common root. This is best shown with an example.
[edit] Examples
[edit] Example 1: Joe Satriani - Not of This Earth
This song is fully based on the pitch axis of E. The chords E major 13, E minor 7 sharp 5, E major 13, and E 7 suspended 4 imply a transition between E Lydian, E Aeolian, E Lydian, and E Mixolydian. This pattern continues throughout the song, keeping a strong feel of tonality while changing through the modes in a rather disorienting way.
The chord E minor 7 sharp 5 is not a perfect match for E Aeolian. When spelling out the mode to use over this chord, instead of thinking of the chord as E minor 7 sharp 5 (E-F#-G-A-B#-C-D-E), think of it as E minor 7 add 6 (E-F#-G-A-B-C-D-E). Otherwise, the E diminished scale might be a good choice (E-F#-G-A-A#-C-C#-D#-E)
It is also important to note than in conventional music theory, there is no such thing as an Eminor 7 sharp 5 chord. This chord (spelled E, G, C and D) is really a first inversion C major chord with an added 9th (the D), which could also be thought of as a C major chord with an E in the bass, or C/E. From here you could choose to use either a C Ionian or Lydian scale, which would correspond to an E Phyrgian or E Lydian respectively. Whilst this might seem to be making the chord more complicated, it also helps to explain the relative lack of tension and 'major' sound of the chord.
[edit] Example 2: Dream Theater - Lie
The break in Dream Theater's "Lie" is built on Pitch Axis Theory. The bassist plays B while the guitarist and keyboardist imply the chords in the progression: B minor, B minor 7, C# dominant 7, and E minor.
The scales used for each of these four chords are B Aeolian(natural minor), B Dorian, C# Mixolydian, and E Aeolian, respectively. However, as these are all diatonic modes, they can all be thought of as being based on the root of B. If the scales are shifted to start on B, then the progression appears as B Aeolian, B Dorian, B Lydian, and B Phrygian.
[edit] Artists who use pitch axis theory
These artists use pitch axis theory and shifting modes in their music.
