I was told once that carny style calliopes were frequently "played in fifths" because it was just sufficiently irritating to discourage rational thinking so that the customers would take more wild chances and spend more of their money on the (always) rigged games.

The comment was a rather offhand one, but came from a fairly advanced university music student, at a time when I knew even less (if that's possible) about music theory than now. He could have been "yanking my chain," but I took it then as an honest observation on the amusement park (and constantly annoying calliope) where our choir was partying.

John