The neo-Pythagoreans reportedly held that there were Pythagorean doctrines concealed in Plato's dialogues (Ch. 1). This section shows that they also encouraged students of Plato to learn about the twelve-note musical scale, quarternotes and the theory of consonance.

Theon's book On the Mathematics Useful for Reading Plato has been somewhat neglected by historians of philosophy. It seems to be a general introduction to mathematics, music and astronomy, and does little to connect these to specific passages in Plato's dialogues. Although typical of much Pythagoreanizing Platonism in antiquity, it of ers a fascinating and relatively early window on to the resurgence of interest in Plato around the first century, even if Theon ot en discusses topics that seem to have little relevance to Plato. The following passages show that his music theory is useful for unravelling Plato's allegory.

Theon (fl. 100 ce) was a compiler and included long passages from an earlier lost work by the neo-Pythagorean Thrasyllus (died 36 ce). He is usually identified with the Egyptian Greek who became the court philosopher to the Roman emperor Tiberius and organized Plato's dialogues into the tetrologies still used in some editions today. Tarrant studied h rasyllus' relation to the developing tradition of Platonism in his Thrasyllan Platonism (1993) and his Plato's First Interpreters (2000).