This chapter studies the first of three of Plato’s afterlife myths treated in this book, namely the Spindle of Necessity from the Myth of Er in the Republic. The Spindle is a representation of the planetary orbits, along with the sound they are said to produce, which we know as the harmony of the spheres. The author argues against the traditional interpretation of this harmony as an octave scale, arguing instead for the Spindle as an anticipation of the harmonic series. In this she has called upon evidence for ancient recognition of tones as composite, and for the use of harmonics in ancient performance practice. This is important because, as she argues, Plato is striving toward an abstract, mathematical framework for consonance, which, further, carries ethical connotations. Combining as it does astronomy and music, the Spindle represents the role of sound and vision in shaping our understanding of the cosmos of which the soul is a part. Musical concord acts as a blueprint for the souls’ right ethical conduct during incarnation, which ought to follow natural laws, among which is the law of harmony. In the Myth of Er, the human soul is privileged to a vision of concord, in order to understand what to strive for.