According to Fludd “the monochord is the internal principle which, from the centre of the whole, brings about the harmony of all life in the cosmos”. By altering the tension of the strings, God, the “Great Chord”, is able to determine the density of all materials between Empyreum and Earth. The instrument is divided in half into an upper, ideal, active octave and a lower, material, passive octave, and these are in turn divided into fourths and fifths. On these intervals the upper, principle of light moves down into dark mater, and at their intersection the sun assumes the power of transformation. Robert Fludd, Utriusque Cosmi, Vol. I, Oppenheim, 1617