Ian Brown. Music of the Spheres.

It seemed clear to the Pythagoreans that the distances between the planets would have the same ratios as produced in harmonious sounds in a plucked string. To them, the solar system consisted of ten spheres revolving in circles about a central fire, each sphere giving off a sound the way a projectile makes a sound as it swished through the air: the closer spheres gave lower tones while the farther moved faster and gave higher pitched sounds. All combined into a beautiful harmony, the music of the spheres.