Where you are, perhaps. Here in the States, we pronounce our Rs. For (most of) us 'Murricans, it would rhyme with “mommy.”
Michael Flanders was one of the cleverest lyricists ever. All of his songs, and his introductions to them, are laden with clever wordplay. I gave just one example here:
My father had the “At the Drop of a Hat” records when we were kids, and growing up with them, I took them completely for granted. It was only decades later, when I had become a writer and editor, that I became fully aware just how sophisticated Flanders and Swann’s silly little songs were.