Hughes
In the retrogression of harmonies, a key-note and its trinities, by sounding the same tones as when ascending, leads the ear to the same notes, and the root of each key-note becomes the fifth lower key-note. F, the root of C, becomes key-note; B?, the root of F, the next key-note, and so on. [Harmonies of Tones and Colours, Diagram VII - The Modulating Gamut of the Twelve Keys1, page 29]
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