Until the late renaissance music theory included a field devoted to what was called "speculative music"; in these, sometimes esoteric, studies music was not considered only an esthetic undertaking, but a key for understanding the workings of the world, a "mirror" (speculum in Latin) of the universe. Within this vast field the followers of the so-called "Harmonical Tradition" - strongly influenced by the Pythagoreans - considered the ordering based on the harmonic series as the most important one. Kepler, the last great exponent of that tradition, in his monumental "Harminice Mundi" (The Harmony of the World) has shown, for instance, that the speeds of the planets in the solar system are ordered according to the harmonic intervals ( a discovery that up to this day had to be corrected only m