Note 11 — § 18. The Perfect System.
Reading edition
The epigram is quoted in the pseudo-Euclidean Introductio, p. 19 (Meib.): ho de (sc. Iôn) en dekachordô lyra (i.e. in a poem on the subject of the ten-stringed lyre):—
tên dekabamona taxin echousa tas symphônousas harmonias triodous; prin men s' heptatonon psallon dia tessara pantes Hellênes, spanian mousan aeiramenoi.
'The triple ways of music that are in concord' must be the three conjunct tetrachords that can be formed with ten notes (b c d e f g a b♭ c d). This is the scale of the Lesser Perfect System before the addition of the Proslambanomenos.