Symmetrical scales offer unique harmonic possibilities due to their regular interval patterns. Unlike diatonic scales, their symmetrical construction allows for fascinating modal interchange techniques and harmonic colors that can add depth to your compositions.
In this interactive exploration, we'll focus on three primary symmetrical scales:
Each of these scales has a limited number of unique transpositions due to their symmetrical nature, creating interesting opportunities for modal interchange.
Modal interchange (or modal mixture) traditionally involves borrowing chords from parallel modes. With symmetrical scales, the approach is slightly different due to their unique properties:
The octatonic (diminished) scale has only three unique transpositions, and each contains 8 notes. This creates rich possibilities for borrowing chords:
Example: A C half-whole diminished scale (C, D♭, E♭, E, F♯, G, A, B♭) contains:
This creates fascinating interchange possibilities between these keys.
The hexatonic (augmented) scale has four unique transpositions, each containing 6 notes. The augmented scale can be viewed as two augmented triads a half-step apart:
Example: A C augmented scale (C, E, G♯, D♭, F, A) contains:
The whole tone scale has only two unique transpositions, each containing 6 notes. Each whole tone scale contains:
The diminished scale offers a wealth of harmonic possibilities that create unique colors:
| Scale | Common Uses | Chord Types |
|---|---|---|
| Half-Whole Diminished | Over dominant 7th chords | dom7, dim7, m6, m7♭5, 7♭9 |
| Whole-Half Diminished | Over diminished chords | dim7, m7♭5, maj7♯5 |
The augmented scale creates a floating, ambiguous tonality with multiple tonal centers:
| Property | Harmonic Implication |
|---|---|
| Symmetry at minor third intervals | Allows for smooth modulation between keys a minor third apart |
| Contains two augmented triads | Creates tension and ambiguity in tonal center |
The whole tone scale creates a floating, dreamlike quality due to its lack of semitones:
| Property | Harmonic Implication |
|---|---|
| No perfect 5th intervals | Creates tonal ambiguity and tension |
| Contains tritones | Provides unstable, tension-filled sound |
Experiment with modal interchange using symmetrical scales to create unique chord progressions:
Advanced Concept: Symmetrical scales can create what's known as "multi-tonic systems" where multiple tonal centers coexist without a clear hierarchy. This concept was explored by composers like Bartók, Stravinsky, and in jazz by musicians like John Coltrane.
Symmetrical scales provide a rich palette of harmonic colors that extend beyond traditional diatonic harmony:
Modal interchange with these scales allows for:
By understanding the theoretical underpinnings of these scales and experimenting with their harmonic implications, composers and improvisers can access a world of harmonic color beyond conventional tonal harmony.