Aristides Quintilianus' dates are not known, but he can hardly be earlier than the first century A.D. or later than the third. Several passages in the early pages of his deMusica1 purport to record facts about the practice of much older theorists, in contexts which make it clear that his references are to the period before Aristoxenus. Since our knowledge of music theory in that period is extremely sketchy, it is obviously worth trying to assess the reliability of Aristides' information. Two of his references have often been recognized as being of special interest, and there is a third, to which, I shall argue, the other two are intimately related. The first (12. 12 to the end of the diagram on 13) records two systems of notation, alleged by Aristides to have been used by oί ⋯ρχαîoι. The second (18. 5 to the end of the diagram on 20) is the famous, or notorious, account of certain ‘divisions of the tetrachord’ which were employed by oί π⋯νυαλαιότατoι πρ⋯ς ⋯ρμoνίας. It is these, Aristides tells us, which are mentioned by Plato in the Republic.2 The remaining passage (15. 8–20) is superficially rather less exciting: it records the names and initial notes of the ⋯ρμoνίαι, or forms of octave scale, said to have been distinguished by oί παλαιoί, and says something about a method by which the πoιότης of each can be made clear. The information given here about the nature of the ⋯ρμoνίαι is familiar: it is to be found, for example, in Cleonides Eisagoge 19. 4 ff., where rather more detail is given, and where the names of the ⋯ρμoνίαι are again ascribed to oί ⋯ρχαîoι (19. 7: cf. also ‘Bellerman's Anonymous’ 62). I shall suggest, however, that Aristides' version has independent interest. What he tells us in the first two passages is found nowhere else.