Harmonic horoscopes are based on principles of resonance, like overtones, which are present in every horoscope. The whole zodiac (360°) is taken as the basic tone, representing the number one (1). By using a higher vibration, we can 'cause' the circle to oscillate more quickly, so to speak, and investigate which planets work together in this particular pattern. For example, the fourth harmonic would involve all those planets which share square aspects (90° - division of the circle by four). In the harmonic chart, these planets form conjunctions. The number corresponding to each 'vibration' influences the interpretation.
At the risk over oversimplifying, one can say that the study of harmonics greatly extends and differentiates the theory of aspects.
Numerical Symbolism and Aspects
The aspects imply favorable, unfavorable or ambivalent relationships between the planets. Although the interpretation depends greatly on the nature of the planets involved, this view largely derives from the traditional symbolism of the numbers 1,2,3 and 4: When the circle is divided by the number one, the result is again 360° or 0° - the distance which defines a conjunction. Division by 2 gives us 180° (Opposition); division by 3 gives us the trine(120°), When we divide by 4 we have a square (90°).
number one symbolizes the original oneness of all being, and consequently
two planets in conjunction become a unified whole. The number two
is the division of this one-ness into polarities, for example male
and female, upper and lower, yin and yang, etc., leading to a certain
tension of opposites. The number three symbolizes a creative striving
' thesis and antithesis leading to a synthesis. Usually, planets
in trine are in the same element. Accordingly, they support and
complement each other.
The number four is matter made manifest, law fulfilled, that which
has become. The corresponding square is generally considered difficult,
each side obstructing the other, unable to give way.
Minor Aspects and Harmonics
Considering the above, we might well wonder about the division of the circle by other numbers, for example 5, 6, 7, 8, 9 and 10. This is as far as the minor aspects go, giving us the quintile, sextile, septile, octile, novile and decile aspects. However, these aspects and their multiples can only be arrived at by calculation. Also, the interpretation of the minor aspects is by no means as clear as that of the major aspects.
Using the technique of harmonics, one can concentrate on a certain division of the circle, instead of searching for minor aspects. The division of the circle is a matter of choice, e.g. by 5, by 57 or by 228, and one should be aware of the symbolic meaning of the number one chooses. Using the chosen number, for example 36, one can calculate a sort of auxiliary horoscope, which can be used for further analysis.
Using the 36th harmonic chart, one can immediately see which planets form 10°-angles (360 : 36 = 10), since all of these planets will stand in conjunction. One could for example take the number 36 as indicative of an ability of fine problem solving: 36=(2x2)x(3x3), as a tension between opposites and the striving for solution multiplied many times. In that case, the 36th harmonic would tell us about someone's approach to problem-solving and of the difficulties to be reckoned with. Within the 36th harmonic one can use major aspects, one can compare the harmonic and the natal charts, one can relate transits to the harmonic positions to events, etc. Finally, the 36th harmonic can be related to the 36th year of life - since it is the 36th time one has completed the journey around the sun, the person will be sensitive to this frequency.
When working with harmonics, one of the difficulties one meets with lies in determining the particular significance of each harmonic, in other words, in finding out what the symbolic value of the numerical factor is. In practice, one usually reduces the numbers in question to multiples of those numbers whose interpretation is assured ' as in the above-mentioned example. Another means of arriving at the meaning of the higher values is to resort to cross-sums and other mathematical and numerological practices. In theory, one could calculate an endless number of harmonic horoscopes for each natal chart. One is left with the choice of resorting to a vague numerological mysticism or working toward a systematic evaluation of the subject through comparative study.
John M. Addey, Harmonics in Astrology, Fowler & Co. The most comprehensive work on this subject, with detailed instructions regarding the calculation, interpretation and application of harmonics.
Michael Harding u. Charles Harvey, Working with Astrology, Arkana 1990, An introduction to harmonics which is easy to read, with lots of practical examples. A great practical guide.
David Hamblin, Harmonic Charts, Aquarian Press. John Addey thought it was important too, as he wrote the foreword.