John O'Dreams uses the tune of Tchaikovsky's 6th Symphony, 1st movement, but possibly Tchaikovsky got it from a folk singer. Only the timing is changed slightly.
As for Carousel "You'll Never Walk Alone" and Gerry Marsden's version: changed from 4/4 to 6/8: makes it easier to sway and wave your lighters to!
Andy 7, I mentioned several comparatively modern songs that have become "standards" further up the thread: perhaps the writers didn't set out to write one, but they surely hoped they might become so.