Addey's Harmonics in Astrology, published in 1976, set out the full theory. Its central idea is that every astrological chart can be analyzed the way a sound can, as a fundamental circle carrying overtones: divide the 360 degree circle by two, three, four, five and so on, and each division, each harmonic, sorts the planets into a new arrangement whose symmetries carry meaning. Traditional aspects fall out as special cases, the conjunction, opposition, trine and square belonging to the low harmonics, while higher divisions reveal patterns the old aspect doctrine never named. Addey argued that this single principle, whole number division of the circle, underlay zodiac signs, aspects and much else, and that astrology's scattered rules were fragments of one harmonic order.
The book reshaped research astrology in Britain and beyond. Harmonic charts entered general practice, the approach converged intriguingly with the vibrational divisions long used in Indian astrology, notably the navamsa and other varga charts, and later researchers, including the Gauquelin reanalyses, worked in explicitly harmonic terms. Mainstream science has not accepted that the claimed wave patterns survive rigorous statistical scrutiny, and astrology's empirical standing remains what it was; but within the discipline Addey's harmonics stand as the twentieth century's most ambitious attempt to unify it, and the atlas records him as its founder.