Plato, Laws 722d

νόμους δὲ ἄρτι μοι δοκοῦμεν λέγειν ἄρχεσθαι, τὰ δʼ ἔμπροσθεν ἦν πάντα ἡμῖν προοίμια νόμων. τί δὲ ταῦτʼ εἴρηκα; τόδε εἰπεῖν βουληθείς, ὅτι λόγων πάντων καὶ ὅσων φωνὴ κεκοινώνηκεν προοίμιά τέ ἐστιν καὶ σχεδὸν οἷόν τινες ἀνακινήσεις, ἔχουσαί τινα ἔντεχνον ἐπιχείρησιν χρήσιμον πρὸς τὸ μέλλον περαίνεσθαι. καὶ δή που κιθαρῳδικῆς ᾠδῆς λεγομένων νόμων καὶ πάσης μούσης προοίμια θαυμαστῶς

yet it is only recently that we have begun, as it seems, to utter laws, and what went before was all simply preludes to laws. What is my object in saying this? It is to explain that all utterances and vocal expressions have preludes and tunings-up (as one might call them), which provide a kind of artistic preparation which assists towards the further development of the subject. Indeed, we have examples before us of preludes, admirably elaborated,