What is ironic about the narrators statement “lodge meeting nights , more and more often they had him to lead the singing”?

Ironically, what the wife and everyone else failed to notice was that the "singing" was the howl of a "werewolf".

Lodge Meeting nights, more and more often they had him to lead the singing. He had such a beautiful voice, and he’d lead off strong, and the others following and joining in, high voices and low. It brings the shivers on me now to think of it, hearing it, nights when I’d stayed home from meeting when the children was babies — the singing coming up through the trees there, and the moonlight, summer nights, the full moon shining. I’ll never hear anything so beautiful. I’ll never know a joy like that again.