Plato, Laws 660b

νῦν οὖν οὕτω δοκοῦσίν σοι, πρὸς Διός, ὦ ξένε, ἐν ταῖς ἄλλαις πόλεσι ποιεῖν; ἐγὼ μὲν γὰρ καθʼ ὅσον αἰσθάνομαι, πλὴν παρʼ ἡμῖν ἢ παρὰ Λακεδαιμονίοις, ἃ σὺ νῦν λέγεις οὐκ οἶδα πραττόμενα, καινὰ δὲ ἄττα ἀεὶ γιγνόμενα περί τε τὰς ὀρχήσεις καὶ περὶ τὴν ἄλλην μουσικὴν σύμπασαν, οὐχ ὑπὸ νόμων μεταβαλλόμενα ἀλλʼ ὑπό τινων ἀτάκτων ἡδονῶν, πολλοῦ δεουσῶν τῶν αὐτῶν εἶναι καὶ κατὰ ταὐτά, ὡς

In Heaven’s name, Stranger, do you believe that that is the way poetry is composed nowadays in other States? So far as my own observation goes, I know of no practices such as you describe except in my own country and in Lacedaemon; but I do know that novelties are always being introduced in dancing and all other forms of music, which changes due not to the laws, but to disorderly tastes and these are so far from being constantly uniform and stable—like the Egyptian ones you describe—that they are never for a moment uniform.