Plato, Laws 657b

σεσωμένα χρόνον μέλη τῆς Ἴσιδος ποιήματα γεγονέναι. ὥσθʼ, ὅπερ ἔλεγον, εἰ δύναιτό τις ἑλεῖν αὐτῶν καὶ ὁπωσοῦν τὴν ὀρθότητα, θαρροῦντα χρὴ εἰς νόμον ἄγειν καὶ τάξιν αὐτά· ὡς ἡ τῆς ἡδονῆς καὶ λύπης ζήτησις τοῦ καινῇ ζητεῖν ἀεὶ μουσικῇ χρῆσθαι σχεδὸν οὐ μεγάλην τινὰ δύναμιν ἔχει πρὸς τὸ διαφθεῖραι τὴν καθιερωθεῖσαν χορείαν ἐπικαλοῦσα ἀρχαιότητα. τὴν γοῦν ἐκεῖ οὐδαμῶς ἔοικε δυνατὴ γεγονέναι διαφθεῖραι, πᾶν δὲ τοὐναντίον.

all this lapse of time are the compositions of Isis. Hence, as I said, if one could by any means succeed in grasping no principle of correctness in tune, one might then with confidence reduce them to legal form and prescription, since the tendency of pleasure and pain to indulge constantly in fresh music has, after all, no very great power to corrupt choric forms that are consecrated, by merely scoffing at them as antiquated. In Egypt, at any rate, it seems to have had no such power of corrupting,—in fact, quite the reverse.