The particle de (δέ) of I.18.356 is syntactically correlated with the particle men (μέν) in a preceding verse, I.18.354. But a rhapsode (rhapsōidos) could begin his performance with the de-clause, thus “stranding,” as it were, the preceding men-clause. Here is an example, with reference to the performance of a rhapsode in the Ptolemaic era of Alexandria:
καὶ ὁ μὲν ῥαψῳδὸς εὐθὺς ἦν διὰ στόματος πᾶσιν, ἐν τοῖς Πτολεμαίου γάμοις ἀγομένου τὴν ἀδελφὴν καὶ πρᾶγμα δρᾶν ἀλλόκοτον <νομιζ>ομένου καὶ ἄθεσμον ἀρξάμενος ἀπὸ τῶν ἐπῶν ἐκείνων·
Ζεὺς δ᾿ Ἥρην ἐκάλεσσε κασιγνήτην ἄλοχόν τε [I.18.356]
The rhapsode [rhapsōidos] was the talk of everybody—the one who, at the wedding of Ptolemy who, in marrying his own sister was considered to be committing a deed unnatural and unholy, began with the following words: ‘And [de] Zeus summoned Hērā his sister, his wife’ [I.18.356]
Plutarch Table Talk 736e
The historical occasion is the wedding, in the first quarter of the third century before our era, of Ptolemy II Philadelphus to his sister, Arsinoe, in accordance with the practice of Egyptian pharaohs—and in violation of Hellenic practices. Evidently, then, the particle de could be used to begin a rhapsodic performance, even in contexts were such a use was dependent on a preceding men-clause. For an example of such a de at the beginning of a Homeric rhapsody, see the comment on O.03.001.