Pickman's model
Starry Wisdom
yeh carousel, grease or the sound of music this ain'tA musical switches between two different modes: standard drama and song. The characters suddenly burst into song in situations where they wouldn't in real life. In the Wicker Man, there's no mode-switching. The characters are singing because they're singing. Even the naked Britt Eckland bit, albeit the singing is a bit weird, but that's the idea: we're supposed to accept that she really is singing.