Mode-based Hexatonic Scales in Music Theory
In the world of music theory, a hexatonic scale is a musical scale consisting of six distinct notes. While the common seven-note diatonic scale forms the basis of much Western music, hexatonic scales offer a unique tonal palette used across various global traditions and genres.
These scales can be constructed through different methods, such as removing specific notes from a standard scale or combining multiple triads—groups of three notes built in thirds—that do not share any common tones.
Foundational Hexatonic Scales
The two most common variations are the major and minor hexatonic scales. The major hexatonic scale is created by taking a standard major scale and removing the seventh note. For example, in the key of C, the notes would be C, D, E, F, G, and A. Alternatively, this scale can be formed by superimposing two mutually exclusive triads, such as C major (C, E, G) and D minor (D, F, A).
The minor hexatonic scale is derived from a minor scale by removing the sixth note. In the key of C, this results in the notes C, D, E♭, F, G, and B♭.
Hexatonic Scales in Folk Traditions
Six-note scales are prevalent in many folk traditions, particularly in Irish and Scottish music. These scales are often described by omitting the fourth or sixth note of a seven-note diatonic scale. Another common construction method involves adding two triads that are a tone apart; a prime example of this is found in the song "Shady Grove," which utilizes A minor and G major triads.
Modal Variations of the Hexatonic Scale
Just as diatonic scales have modes, hexatonic scales can be shifted to create different tonal centers and moods. Each mode is based on a specific parent scale with one note omitted.
| Mode | Name | Notes | Based on Mode | Omitted Note |
|---|---|---|---|---|
| I | Major hexatonic | 1 2 3 4 5 6 | Ionian | 7 |
| II | Minor hexatonic | 1 2 ♭3 4 5 ♭7 | Mixolydian | 6 |
| III | Ritsu Onkai | 1 ♭2 ♭3 4 ♭6 ♭7 | Dorian | 5 |
| IV | Raga Kumud | 1 2 3 5 6 7 | Aeolian | 4 |
| V | Mixolydian hexatonic | 1 2 4 5 6 ♭7 | Phrygian | 3 |
| VI | Phrygian hexatonic | 1 ♭3 4 5 ♭6 ♭7 | Locrian | 2 |
Key Facts
- Definition: A hexatonic scale contains six notes.
- Major Construction: Formed by removing the 7th note of a major scale or combining two exclusive triads.
- Minor Construction: Formed by removing the 6th note of a minor scale.
- Cultural Use: Widely used in Scottish and Irish folk music.
- Modal Diversity: Includes specialized scales such as Ritsu Onkai and Raga Kumud.
Frequently Asked Questions
What is the difference between a diatonic and a hexatonic scale?
A diatonic scale consists of seven notes per octave, whereas a hexatonic scale consists of only six notes.
How can I build a major hexatonic scale using triads?
You can create a major hexatonic scale by superimposing two mutually exclusive triads, such as a C major triad (C, E, G) and a D minor triad (D, F, A).
Which note is removed to create a minor hexatonic scale?
The minor hexatonic scale is created by removing the sixth note from a standard minor scale.
Where are hexatonic scales commonly found in traditional music?
They are frequently used in Irish and Scottish folk traditions, often constructed by omitting the fourth or sixth note of a diatonic scale.
What is Ritsu Onkai?
Ritsu Onkai is the third mode of the hexatonic system, based on the Dorian mode with the fifth note omitted.