Passage 10.30.9
ὑπὲρ τούτου ἐστὶν ἐπὶ πέτρας καθεζόμενος Μαρσύας, καὶ Ὄλυμπος παρʼ αὐτὸν παιδός ἐστιν ὡραίου καὶ αὐλεῖν διδασκομένου σχῆμα ἔχων. οἱ δὲ ἐν Κελαιναῖς Φρύγες ἐθέλουσι μὲν τὸν ποταμὸν ὃς διέξεισιν αὐτοῖς διὰ τῆς πόλεως ἐκεῖνόν ποτε εἶναι τὸν αὐλητήν, ἐθέλουσι δὲ καὶ εὕρημα εἶναι τοῦ Μαρσύου τὸ Μητρῷον αὔλημα· φασὶ δὲ ὡς καὶ τὴν Γαλατῶν ἀπώσαιντο στρατείαν τοῦ Μαρσύου σφίσιν ἐπὶ τοὺς βαρβάρους ὕδατί τε ἐκ τοῦ ποταμοῦ καὶ μέλει τῶν αὐλῶν ἀμύναντος.
Above this stands Marsyas seated upon a rock, and near him Olympus is depicted in the form of a handsome youth learning to play the flute. The Phrygians at Celaenae claim that the river which flows through their city was formerly that very flute-player; they also assert that the flute-melody sacred to the Mother was Marsyas' invention. Furthermore, they say that Marsyas repelled the invasion of the Galatians by coming to their aid against the barbarians, using both the water from the river and the music of his flutes.