φωνὴν ἴσκουσ’ ἀλόχοισιν.
‘She [= Helen] was likening [eïskein] her voice to the voices of their wives.’
Helen possesses the art of ‘making a likeness’ of the voices of others. By ‘likening’ her voice to the voices of any wife of any Homeric hero, she is actually making her voice the same as theirs. We see here a Muse-like feat of verbal art. On this point, I have more to say in the comment on O.19.203.