There is a correlation between the nature of the soul and the nature of the world, and the harmonies of music derive from this correlation, and when we hear music that springs from this nature it tempers the mind and brings it to its natural order and rest. This is why music can restore the mind and heart. Since harmonies are relationships of numbers, and since beauty shines most clearly in what is unified and whole, the most simple, unified and whole numbers produce harmonies, while complex numbers produce discords. Discords have a place in music, but only when they are resolved to harmonies. The telos or pull of a discord is the harmony it naturally resolves to.
Music therefore moves from simplicity and elaborates in complexity, and then returns to simplicity.
This is the natural motion of music. It moves in a circle and returns to where is began. This is reflected in another way. Music begins in silence, manifests in sound, and finally returns to silence. The basis of music is the scale.