Heptatonic Scale - Heptonia Prima and Secunda

Heptonia Prima and Secunda

The rather unwieldy name of Heptonia Prima and Heptonia Secunda are given to the various seven-note scales which can be formed using tones and semitones but without two semi-tones appearing in succession. Some are more theoretical than others. They are

Heptonia Prima

Beginning on keynote A and working up the notes of the 'natural minor' scale (A, B, C, D, E, F, G, A), the seven modes are:

• Aeolian mode (natural minor) t-s-t-t-s-t-t

• Locrian mode s-t-t-s-t-t-t

• Ionian Mode (major) t-t-s-t-t-t-s

• Dorian Mode t-s-t-t-t-s-t

• Phrygian Mode s-t-t-t-s-t-t

• Lydian Mode t-t-t-s-t-t-s

• Mixolydian Mode t-t-s-t-t-s-t

It may be noted that the Dorian is exactly the same descending as ascending. The less common series is

Heptonia Secunda

The difference between this and the diatonic modes is that they have two and three tones between each semitone, while these latter modes have one and four. These are sometimes called modes of the melodic ascending minor since that is the most commonly used scale of this type, but other modes can be produced by starting on the different scale notes in turn. Thus starting on keynote A as above and following the notes of the ascending melodic minor (A, B, C, D, E, F♯, G♯) yields these seven modes:

• 'Melodic ascending minor' t-s-t-t-t-t-s
• 'Phrygian raised sixth' s-t-t-t-t-s-t combines the Phrygian flat second and Dorian raised sixth
• 'Lydian raised fifth' t-t-t-t-s-t-s combines the Lydian fourth with a raised fifth

• 'Acoustic' or 'Lydian Dominant' Scale t-t-t-s-t-s-t So-called because close to the scale built on natural overtones and combines Lydian raised fourth with Myxolydian (Dominant) flat seventh
• 'Major minor' scale t-t-s-t-s-t-t Like natural minor (aeolian) but with a major third

• 'Half diminished scale' or 'Locrian sharp 2' scale t-s-t-s-t-t-t This is like the Locrian with a raised second

• 'Altered scale' s-t-s-t-t-t-t Like Locrian with diminished fourth

These modes are more awkward to use than those of the diatonic scales due to the four tones in a row yielding augmented intervals on one hand while the one tone between two semitones gives rise to diminished intervals on the other. For example, the last two modes listed above both have 'Locrian' diminished triads built on their tonics given them unstable tonality while the third mode not only has an augmented fourth a la the Lydian mode but also an augmented fifth making the dominant and subdominant unusable.