# Correspondence

noun: compatibility of observations ("The results of two tests were in correspondence")
noun: similarity by virtue of correspondence
noun: the relation of correspondence in degree or size or amount
noun: (mathematics) an attribute of a shape or relation; exact correspondence of form on opposite sides of a dividing line or plane
noun: a function such that for every element of one set there is a unique element of another set

Principle of Correspondence
"This Principle embodies the truth that there is always a Correspondence between the laws and phenomena of the various planes of Being and Life. The old Hermetic axion ran in there words: "As above, so below; as below, so above." And the grasping of this Principle gives one the means of solving many a dark paradox, and hidden secret of Nature. There are planes beyond our knowing, but when we apply the Principle of Correspondence to them we are able to understand much that would otherwise be unknowable to us. This Principle is of universal application and manifestation, on the various planes of the material, mental, and spiritual universe - it is an Universal Law. The ancient Hermetists considered this Principle as one of the most important mental instruments by which man was able to pry aside the obstacles which hid from view the Unknown. Its use even tore aside the Veil of Isis to the extent that a glimpse of the face of the goddess might be caught. Just as a knowledge of the Principles of Geometry enables man to measure distant suns and their movements, while seated in his observatory, so a knowledge of the Principle of Correspondence enables Man to reason intelligently from the Known to the Unknown. Studying the monad, he understands the archangel." [The Kybalion; San Francisco, 1904]

One of the many ways to use this principle is to know that one discrete pitch in one octave is equivalent to another pitch in any other octave - insofar as relative pitch or interval goes. A "C" in one octave is equivalent to "C" in any other octave regardless of specific frequency. In this case the relationship is of the octave or a doubling or halving of frequency. This relativity of relationship holds for any other manifestation of rhythmic energies set in octave relations such as color, music tones, cycles of all kinds and what have you.

Ramsay
It is in their inverse relations that the major and the minor are equal. Every note, chord, and progression in the one has its reciprocal or corresponding note, chord, and progression in the other. This is the Law of Duality. And this general law of Nature is so deeply rooted in music, that is the numbers which represent the vibrations in the major system be made to represent quantities of string, these quantities will produce the minor system (beginning, of course, with the proper notes and numbers); so that when the quantities are minor the tones are major, and when the quantities are major the tones are minor.1[Scientific Basis and Build of Music, page 44]

Hughes
"Comparing wave-lengths of light with wave-lengths of sound—not, of course, their actual lengths, but the ratio of one to the other—the following remarkable correspondence at once comes out:—Assuming the note C to correspond to the colour red, then we find that D exactly corresponds to orange, E to yellow, and F to green. Blue and indigo, being difficult to localise, or even distinguish in the spectrum, they are put together; their mean exactly corresponds to the note G: violet would then correspond to the ratio given by the note A. The colours having now ceased, the ideal position of B and the upper C are calculated from the musical ratio." [Harmonies of Tones and Colours, On Colours as Developed by the same Laws as Musical Harmonies2, page 19]

"Our aim is to promote that agreement by showing the correspondence between truly scientific conclusions and Holy Writ; by making it plain that scientific truths, like spiritual, have for ever been descending from heaven to man."— [J. W. Reynolds, M.A.] [Harmonies of Tones and Colours, Reflections on the Scheme4, page 46]