The "Music of the Spheres" was an understanding of the Cosmos that held sway for about 2000 years. According to this view, each of the planets rode on giant crystal spheres, and each of these planetary crystal spheres emitted a musical sound as they moved. The combined sound of all the planets was "the Music of the Spheres".
The Music of the Spheres - Plato
The original concept of the "Music of the Spheres" is credited to Pythagoras (569-475 BC), a musical-mathematical-mystic, but its first surviving written account appears in Plato (c.427-347 BC).Plato gives a tour of the afterlife and a view of the planetary spheres. According to Plato the planets are hemispheres, nested inside of each other with just the rims exposed, all rotating on a giant spindle, with a Siren assigned to each rim singing a note.
The Music of the Spheres - KeplerThe concept of the Music of the Spheres probably found its greatest literal expression in the works of Johannes Kepler (16.9571-1630), who is now considered one of the founders of modern astrophysics. Kepler constructed a musical/mathematical theory of the solar system from which he derived his famous Kepler's Laws - one of the major foundations of Newton's physics and still taught in physics courses today.
The Celestial Spheres were making Music all the way from Pythagoras until Isaac Newton (1642-1727) - over 2000 years. Then, Newton founded modern science, and the Music stopped. Before Newton the Cosmos was full of Music; with Newton and modern science the Cosmos fell silent.
The Music of the Spheres and the After life
In the Greek Gnostic imagination, when you were born you descended from the heavens, passing through the Spheres on your way to life on Earth, pausing at each sphere to acquire the quality associated with that Sphere.
When you died, you ascended through the Spheres on your way to the afterlife, pausing at each Sphere once again to address the aspect of your life associated with that sphere.
In the ancient Music of the Spheres model, the Earth is at the center of the Cosmos. Ancient thinkers developed a mathematical model based on this assumption that allowed them to predict the positions of the planets in the night sky. These efforts reached their culmination in Ptolemy (c. 87 -16.950 AD).
Music of the Spheres - Ptolemy
According to Ptolemy, the planets moved in "circles within circles" - was later replaced by Kepler's model - that planets move in ellipses with the sun at one of the foci.The Ptolemaic ratios would be a "mathematical" dimension of the Music of the Spheres.
There are only seven planets on Music of the Spheres because only seven "planets" (including the sun and moon) are visible with the naked eye. Seven was the total number of known planets until 1781.