The Universal Harmonies of all the Six Planets, as if in Common Counterpoint, Occur in Four Partsby Johannes Kepler
These are the names of human voices, and voices and sounds do not exist in the heaven, on account of the absolute quietness of the motions
But not even the phenomena in which we detect the harmonie are comprised in the category of true motion, since in fact we consider only the apparent motions seen from the Sun; and indeed there is no such cause in the heaven, calling for a definite number of voices for making harmony, as there is in human melody.
In fact the number of the 6 planets going round the Sun came first, from the number of the 5 intervals, which were taken from the regular figures; and then afterwards (in the order of Nature not of time) the decision had to be made about the agreement of the motions.
Nevertheless, for some unknown reason this wonderful agreement with human melody forces me so that I am compelled to pursue this part of the comparison also, even without solid natural cause.
For those properties which in Book 3 Chapter 16, custom attributes, and nature appropriates to the bass, are the same as in a sense Saturn and Jupiter hold in the heaven; those of the tenor, we find in Mars; those of the alto belong to the Earth and Venus; and those of the treble are the same as Mercury has, if not in equality of distances, yet certainly in proportion. For when ever in the following Chapter the eccentricities of each planet are de duced from their own proper causes, and through them the proper intervals of the motions of each, that has a wonderful result, and I do not know whether it is not equally intended, and not merely an adjustment to necessities: that I. as bass is opposed to alto, so there are two planets which have the nature of the alto, and two of the bass, just as in any kind of music there is one voice on each side; and in dividual planets have the remaining individual voices.
II. As the alto which is nearly the highest is in a narrow space, for necessary and natural reasons which were explained in Book III, so the planets which are nearly the inmost, the Earth and Venus, have very narrow distances between their motions, the Earth not more than a semitone, Venus not even a d i e s i s .I I I . And as the tenor is free, yet proceeds mod erately, so Mars, with the sole exception of Mercury, can make the greatest distance, that is to say a diapente. IV. And as the bass makes harmonic leaps, so Saturn and Jupiter cover harmonic intervals, and have a distance between each other varying from a diapason to a diapente above the diapason. V. And as the treble is most free, more than all the rest, and the same is also the fastest, so also Mercury can range over more than a diapason and back again very quickly. But let this indeed be by the way: let us now hear the causes of the eccentricities.