Now the melody of spoken language is measured by a single interval, which is very close to that which is called a fifth. When the voice rises towards the acute, it does not rise more than three tones and a semitone; and when it falls towards the grave, it does not fall from this position by more than this interval. However, the whole utterance during one word is not delivered at the same pitch throughout, but one part of it is at the acute pitch, another is at the grave, another is at both. Of the words which have both pitches, some have the grave fused with the acute on the same syllable, and we call these “circumflexed”; others have them falling on separate syllables, and each retains its own quality. ― translation from: Stephen Usher, opere citatoLCL 466 (1985), chapter xi, paragraph 4, page 77, line 24 – page 79, line 5