Passage 9.30.6
ἄλλοις δὲ εἰρημένον ἐστὶν ὡς προαποθανούσης οἱ τῆς γυναικὸς ἐπὶ τὸ Ἄορνον διʼ αὐτὴν τὸ ἐν τῇ Θεσπρωτίδι ἀφίκετο· εἶναι γὰρ πάλαι νεκυομαντεῖον αὐτόθι· νομίζοντα δέ οἱ ἕπεσθαι τῆς Εὐρυδίκης τὴν ψυχὴν καὶ ἁμαρτόντα ὡς ἐπεστράφη, αὐτόχειρα αὐτὸν ὑπὸ λύπης αὑτοῦ γενέσθαι. λέγουσι δὲ οἱ Θρᾷκες, ὅσαι τῶν ἀηδόνων ἔχουσι νεοσσιὰς ἐπὶ τῷ τάφῳ τοῦ Ὀρφέως, ταύτας ἥδιον καὶ μεῖζόν τι ᾄδειν.
But others narrate that when his wife died before him, he journeyed on her account to Aornos in Thesprotia, for there was in ancient times a necromantic oracle there. Believing that Eurydice's soul followed behind him, and erring in turning around, he killed himself from grief. The Thracians claim that those nightingales who nest upon Orpheus' tomb sing sweeter and more powerfully than others.