A music theory manual written by a second century Neo-Pythagorean. It contains one of the earliest known models for the Harmony of the Spheres, a concise analysis of the musical intervals of Timaeus and many other interesting tidbits, including resolving seeming contradictions between Aristoxenian theories on music with Pythagorean theories on music. The analysis by the late Flora R Levin is an invaluable guide through this fascinating document written for an ancient, unnamed princess.