How do sounds reach the soul? How does the soul judge them? How can the movement of a melody be accounted for? These and others are the questions that Porphyry of Tyre tries to answer in his 'Commentary on Claudius Ptolemy's Harmonics'. This book collects the vast amount of philological work that has been carried out on this imposing work since Ingemar Düring's 1932 edition and presents the reader with a reliable and up-to-date text.