Passage 4.33.2
τὸ δὲ ἄγαλμα τοῦ Διὸς Ἀγελάδα μέν ἐστιν ἔργον, ἐποιήθη δὲ ἐξ ἀρχῆς τοῖς οἰκήσασιν ἐν Ναυπάκτῳ Μεσσηνίων· ἱερεὺς δὲ αἱρετὸς κατὰ ἔτος ἕκαστον ἔχει δὲ τὸ ἄγαλμα ἐπὶ τῆς οἰκίας. ἄγουσι δὲ καὶ ἑορτὴν ἐπέτειον Ἰθωμαῖα, τὸ δὲ ἀρχαῖον καὶ ἀγῶνα ἐτίθεσαν μουσικῆς· τεκμαίρεσθαι δʼ ἔστιν ἄλλοις τε καὶ Εὐμήλου τοῖς ἔπεσιν, ἐποίησε γοῦν καὶ τάδε ἐν τῷ προσοδίῳ τῷ ἐς Δῆλον· τῷ γὰρ Ἰθωμάτα καταθύμιος ἔπλετο μοῖσα ἁ καθαρὰ ν κιθάραν καὶ ἐλεύθερα σάμβαλʼ ἔχοισα. Eumelus, unknown location. οὐκοῦν ποιῆσαί μοι δοκεῖ τὰ ἔπη καὶ μουσικῆς ἀγῶνα ἐπιστάμενος τιθέντας.
The statue of Zeus is the work of Ageladas, originally made for the Messenians who inhabited Naupactus. Each year they elect a priest for the image, and he keeps the statue in his own home. They also hold an annual festival, the Ithomaia, and in ancient times they established a competition in music as well. Among other evidence for this are the verses of Eumelus; indeed, he composed these lines too in the Processional Hymn to Delos: "For the Muse who delights in Ithome came with pure lyre and free sandals." Thus it seems to me clear that, since he composed such poetry, he was aware of their musical competition.