Three series of examples successively taken from odes by Pindaros and Bacchylides, from three recognition duets in Euripides (Ion, Iphigenia in Taurus, Helen), and from the parodos of Aristophanes' Thesmoophories reveal, thanks to the account of marked beats, an evenness which in the first two tends to neutralise the triadic composition, and equivalences which, in the other two, reveal underneath an apparent freedom a real architectural construction [Summary, p. 413].