Although I wouldn’t have called it that, I sort of get what the original poster means by “farm” musical if we take “farm” as shorthand for “rural” (i.e., a story set in a farm, on a ranch, by the seaside, etc.).
My father was a sailor stationed in NYC for 6 months in 1943. As a serviceman he was treated to quite a few Broadway shows. He saw Oklahoma a few weeks after the opening. I was shocked to learn that he didn’t care for it! “ I was from the Midwest and I wanted to see the glamorous society life of Cole Porter not cowboys and farmers and girls in gingham.”
