← Encyclopedia of Astrology · lesson 225/235
Harmonic chart
What it is
Every aspect is a whole number dividing the circle. Divide 360° by 2 and you have the opposition; by 3, the trine; by 4, the square; by 5, the quintile; by 6, the sextile. Harmonic astrology takes that idea seriously and builds on it: each number is treated as a theme of its own, and a harmonic chart shows the birth chart "tuned" to one number so that its theme stands out.
The approach was gathered into a system by the British astrologer John Addey (1920–1982), above all in Harmonics in Astrology (1976). Addey re-examined large collections of birth data, including Michel Gauquelin's, and argued that planetary positions showed rhythms based on the division of the circle by whole numbers. His conclusions remain debated, but the harmonic method he set out is widely used.
How it is worked out
To make the Nth harmonic chart, multiply every longitude by N and subtract whole circles until the result lies between 0° and 360°. A planet at 10° Aries (10°) in the 5th harmonic stands at 50°, which is 20° Taurus.
The effect: any two planets that were linked by the Nth harmonic — separated by 360°/N or a multiple of it — land on the same point. In the 5th harmonic chart every quintile and biquintile of the birth chart becomes a conjunction; in the 7th, every septile. The 4th harmonic gathers conjunctions, squares and oppositions into conjunctions, which is why it is read for effort and struggle.
Two cautions follow from the arithmetic. Orbs multiply too, so a harmonic chart is usually read with a tight orb — a degree or two — or it fills with contacts. And because a small error in a planet's position is also multiplied, high harmonics of fast-moving points such as the angles need an accurate birth time.
What the numbers are read as
Interpretations vary between writers, but a common set runs:
- 2nd and 4th — tension, effort, striving; the hard aspects.
- 3rd — ease, enjoyment, what comes naturally; the trine family.
- 5th — skill, style, creative power and the urge to make or shape things.
- 7th — inspiration, imagination, the visionary and the uncanny.
- 9th — fulfilment, peace and joy.
Addey and David Hamblin, who developed the work further, read the harmonics as layers of one chart rather than as separate fortunes: a planet strong in the 5th harmonic shows the kind of thing a person tends to do with flair, not a promise of success.
In other traditions
Vedic astrology has long used divisional charts (vargas) that work in a related way. The best known, the navamsha, divides each sign into nine parts and corresponds closely to the 9th harmonic; it is read especially for marriage and for the deeper strength of a planet.
Keeping it in proportion
Harmonics are an advanced and optional tool. They come alive once ordinary aspects are familiar, since the first twelve harmonics are simply the aspects seen from another angle.
In a reading here
Birth-chart readings here look at the 5th, 7th and 9th harmonics and note planets that come together in them within about a degree, with that harmonic's theme.