Music is not a skill confined to one subject or one season of life. Its usefulness reaches every stage of life, life taken as a whole, and every single action. On this view, a life or an act can be perfectly ordered only through music.
Teaching music to the young is part of forming who they become, not just a pastime. Music bears on the moral life of individuals as well as on their education.
The number ratios that govern musical sound can be set beside the numbers found in the physical world. The analogy suggests that the order heard in music and the order in nature share a common arithmetic.