Plato, Laws 673a

ἐκεῖ δὲ μέλος ἡ τῆς φωνῆς κίνησις. ἀληθέστατα. τὰ μὲν τοίνυν τῆς φωνῆς μέχρι τῆς ψυχῆς πρὸς ἀρετὴν παιδείας οὐκ οἶδʼ ὅντινα τρόπον ὠνομάσαμεν μουσικήν. ὀρθῶς μὲν οὖν. τὰ δέ γε τοῦ σώματος, ἃ παιζόντων ὄρχησιν εἴπομεν, ἐὰν μέχρι τῆς τοῦ σώματος ἀρετῆς ἡ τοιαύτη κίνησις γίγνηται, τὴν ἔντεχνον ἀγωγὴν ἐπὶ τὸ τοιοῦτον αὐτοῦ γυμναστικὴν προσείπωμεν. ὀρθότατα.

motion. Very true. Now the vocal actions which pertain to the training of the soul in excellence we ventured somehow to name music. And rightly so. As regards the bodily actions which we called playful dancing,—if such action attains to bodily excellence, we may term the technical guidance of the body to this end gymnastic.