I suppose it's the way they talk.

I'd give a good deal to be able to understand them.

But still, it's very lovely, isn't it ?" "Ay, like the voices of syrens," said Murgatroyd, speaking for the first time since the _Astronef_ had landed; for this big, grizzled, taciturn Yorkshireman, who looked upon the whole cruise through Space as a mad and almost impious adventure, which nothing but his hereditary loyalty to his master's name and family could have persuaded him to share in, had grown more and more silent as the millions of miles between the _Astronef_ and his native Yorkshire village had multiplied day by day.
"Syrens--and why not, Andrew ?" laughed Redgrave.

"At any rate, I don't think they look likely to lure us and the _Astronef_ to destruction." Then he went on: "Yes, Zaidie, I never heard anything like that before.
Unearthly, of course it is, but then we're not on Earth.

Now, Zaidie, they seem to talk in song-language.