Harmonic Astrology (John Addey)

Harmonic astrology was developed by British astrologer and researcher John Addey (1931-2016), who set forth its principles in his book Harmonics in Astrology (1976). The idea draws on numerical mysticism and musical theory (the concept of harmonics as overtones), transposed into astrology: if the 360-degree zodiacal circle is divided into N equal parts, the result is an Nth-order harmonic. Each harmonic produces its own chart, revealing aspects and configurations invisible in the natal chart.

In practice, it works as follows: in the 4th harmonic (H4), all planetary longitudes are multiplied by 4, and the remainder after division by 360 degrees is taken. This produces a new chart showing the "4th level" — the sphere of structure, stability, and physical reality. The 5th harmonic reveals creativity and joy; the 7th — spirituality and intuition; the 9th — wisdom and subtle ideals; the 12th — limitations and hidden fears. Conjunctions in harmonic charts, corresponding to minor aspects (quintile, septile, etc.) in the natal chart, acquire significance.

Addey also developed "harmonic diagrams" — methods of graphic representation that allow patterns across multiple harmonics to be seen simultaneously. His method attracted the attention of mathematically oriented astrologers and researchers, though it remained on the periphery of mainstream astrological practice due to the complexity of its calculations and interpretation.

In Errarium, harmonic astrology (#44) is the most mathematically formalized astrological system on the platform. Its closest analogue is Ebertin's cosmobiology (#42) as another rationalist approach to astrology. The fundamental difference: Ebertin works with midpoints within the space of a single chart, while Addey mathematically transforms the entire chart into several parallel "dimensions."