This is the one song everyone
would like to learn: the song
that is irresistible ...
Atwood explains on the Poetry Archive site :-
The Sirens had the top halves of women and the bottom halves of birds and they were said to sit on their island and sing so beautifully that anybody who heard them would jump overboard and then they would eat these men. Ulysses was said to have been the only person who ever actually heard the siren song because he made his sailors stuff their ears with wax and he had them tie him to the mast so he wouldn’t jump overboard. But he never told what it was they actually sang, and therefore nobody has ever known. So this is what they actually did sing.