The witches in Shakespeare’s Macbeth equivocate between the demons of random malevolence and ordinary (if exceptionally nasty) old women; and both King James I, whose book on witchcraft may have influenced Shakespeare, and A. W. Schlegel, whose essay on Macbeth certainly influenced Verdi, also stress this ambiguity. In his treatment of Lady Macbeth, Verdi uses certain musical patterns associated with the witches; and like the witches, who sound sometimes tame and frivolous, sometimes like incarnations of supernatural evil, Lady Macbeth hovers insecurely between roles: she is a hybrid of ambitious wife and agent of hell.