Plutarch, Dinner of the Seven Wise Men 150e-f
Aesop quotes a riddling verse about the aulos which Phrygians make from asses’ bones, and which make a better sound than the fawns’ bones which the Phrygians used to use:
διὸ καὶ Κλεοβουλίνη πρὸς τὸν Φρύγιον αὐλὸν ᾐνίξατο·
κνήμῃ νεκρὸς ὄνος με κερασφόρῳ οὖας ἔκρουσεν.
ὥστε θαυμάζειν τὸν ὄνον εἰ παχύτατος καὶ ἀμουσότατος ὢν τἄλλα λεπτότατον καὶ μουσικώτατον ὀστέον παρέχεται.
For this reason Cleobulina told a riddle on the Phrygian aulos:
“With its horn-bearing shin a dead donkey struck me on the ear.”
So one is amazed that the ass – being in other respects most dense and unmusical – provides us with a bone that is most refined and musical.
(The verse is rather corrupt in the manuscripts: I quote the restored version from Babbitt’s Loeb edition.)