‘America,’ said John Updike, ‘is a vast conspiracy for making you happy.’ If that’s true, there have been few more successful conspiracies than the Broadway musical — that is, the ‘book’ (meaning ‘play’) musical — a dramatic form that blends drama of character and narrative with song and dance. ‘Words make you think thoughts, music makes you feel a feeling, a song makes you feel a thought,’ said the songwriter Yip Harburg.