Plato, Laws 765a

μὴ ἔλαττον τετταράκοντα γεγονὼς ἐτῶν. ἱκανὸς δὲ καὶ περὶ μονῳδίαν εἷς, μὴ ἔλαττον ἢ τριάκοντα γεγονὼς ἐτῶν, εἰσαγωγεύς τε εἶναι καὶ τοῖς ἁμιλλωμένοις τὴν διάκρισιν ἱκανῶς ἀποδιδούς. τὸν δὴ χορῶν ἄρχοντα καὶ διαθετῆρα αἱρεῖσθαι χρὴ τοιόνδε τινὰ τρόπον. ὅσοι μὲν φιλοφρόνως ἐσχήκασι περὶ τὰ τοιαῦτα, εἰς τὸν σύλλογον ἴτωσαν, ἐπιζήμιοι ἐὰν μὴ ἴωσιν—τούτου δὲ οἱ νομοφύλακες κριταί—τοῖς δʼ ἄλλοις, ἐὰν μὴ βούλωνται, μηδὲν ἐπάναγκες ἔστω. καὶ

And for solo performances one umpire, of not less than thirty years, is sufficient, to act as introducer and to pass an adequate judgment upon the competitors. The officer and manager of the choirs they must appoint in the following way. All those who are devoted to these subjects shall attend the assembly, and if they refuse to attend they shall be liable to a fine—a matter which the Law-wardens shall decide: any others who are unwilling to attend shall be subject to no compulsion. Every elector must make his nomination from the list of those who are experts: