E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The music or harmony of the spheres. Pythagoras, having ascertained that the pitch of notes depends on the rapidity of vibrations, and also that the planets move at different rates of motion, concluded that the sounds made by their motion must vary according to their different rates of motion. As all things in nature are harmoniously made, the different sounds must harmonise, and the combination he called the harmony of the spheres. Kepler has a treatise on the subject.