ὑΠὸ Πτερύγων: cf. Av.771（“κύκνοι”) “συμμιγῆ βοὴν ὁμοῦ πτεροῖς κρέκοντες ἴακχον Ἀπόλλω . . . ὄχθῳ ἐφεζόμενοι παρ᾽ Ἕβρον ποταμόν”. Clearly Aristophanes means that the voice (“βοήν”) of the swan blended (“συμμιγῆ”) with the accompaniment of the flapping wing. This sense would suit “ὑπό”, which is used from Hesiod onwards for “accompanying” music; see exx. in L. and S. s. v. Il. 1.5. But it was commonly believed that the swan's “song” was made by the noise of the actual wings: cf. Pratin. ap. Athen. 617 C “οἷά τε κύκνον ἄγοντα ποικιλόπτερον μέλος”, Anacr.vii. 8“ἅτε τις κύκνος Καυ?στρῳ”“ποικίλον πτεροῖσι μέλπων”
“ἀνέμῳ σύναυλος ἠχῇ. ὑπὸ πτερύγων” therefore=“πτερύγεσσι”, rather than inter volatum, as Ebeling explains (s.v. “πτέρυξ”); cf. h. Pan 15 “δονάκων ὕπο”, which=“δόναξι”, as Pan could not sing while piping. The music of the swan's wings may have been a conception due to a similar (and correct) belief that the cicala's or grasshopper's “song” was caused by the wings: Hes. Op.583“καταχεύετ᾽ ἀοιδὴν πυκνὸν ὑπὸ πτερύγων”, imitated by Alcaeus fr. 59; cf. Anth. Pal. vii. 192. 1 and 4, 194. 1, 195. 4, 197. 2, 200. 1.
Gemoll's view, that the passage in Aristophanes, quoted above, is the origin of the present line, is most unlikely. References to the swan's song are collected by Voss Myth. Br. ii. p. 112, and Thompson Greek Birds p. 104 f. Aelian (V. H. i. 14) is incredulous.