'The Modes of Ancient Greek Music' by D. B. Monro is a comprehensive exploration of the long-standing controversy surrounding the nature of the ancient musical modes. The author provides a full discussion of the subject, using various sources such as Plato, Aristotle, and Aristoxenus. The book includes information on the early poets, the standard octachord system, the perfect system, the species of a scale, the musical notation, and the remains of Greek music. Monro also analyzes the credibility of Aristides Quintilianus and the evidence for scales of different species. This book is a must-read for anyone interested in ancient Greek music theory and its evolution.