Plato, Laws 670a

κιθαρίσει πλὴν ὅσον ὑπὸ ὄρχησίν τε καὶ ᾠδήν, ψιλῷ δʼ ἑκατέρῳ πᾶσά τις ἀμουσία καὶ θαυματουργία γίγνοιτʼ ἂν τῆς χρήσεως. ταῦτα μὲν ἔχει ταύτῃ λόγον· ἡμεῖς δέ γε οὐχ ὅτι μὴ δεῖ ταῖς Μούσαις ἡμῶν προσχρῆσθαι τοὺς ἤδη τριακοντούτας καὶ τῶν πεντήκοντα πέραν γεγονότας σκοπούμεθα, ἀλλʼ ὅτι ποτὲ δεῖ. τόδε μὲν οὖν ἐκ τούτων ὁ λόγος ἡμῖν δοκεῖ μοι σημαίνειν ἤδη, τῆς γε χορικῆς Μούσης ὅτι πεπαιδεῦσθαι

for the use of either of these instruments by itself is the mark of the mountebank or the boor. Enough, then, of that matter: now as to ourselves. What we are considering is, not how those of us who are over thirty years old, or beyond fifty, ought not to make use of the Muses, but how they ought to do so. Our argument already indicates, I think, this result from our discussion,—that all men of over fifty that are fit to sing ought to have a training that is better than that of the choric Muse.