In some ways the Grand scena e Duetto of Act I is far more of a black sabbath than anything found in the witches’ own music. At the beginning, Verdi notes in the score that the singers must sing in a hushed and dark voice, unless instructed otherwise. Verdi wanted something that was, as far as I know, unprecedented in the domain of nineteenth-century Italian opera, a set-piece that was melodically intense—not recitative—and yet took place in some boundary region between speech and song. A letter of Verdi's to the baritone who created the role of Macbeth, Felice Varesi, makes this point clear: “I’d rather you served the poet better than you serve the composer… . In the grand duet … Note that it's night; everyone is asleep, and this whole duet will have to be sung sotto voce, but in a hollow voice such as to arouse terror.” Verdi was often to repeat this advice. The word hollow (cupa) governed Verdi's whole imagination of Macbeth; it is a subterranean sort of opera, as if the performance were constituted within a cave, or as if the singers each sang from within a private abyss. Indeed words such as cupo and gufo (owl) seem to brood over the text—perhaps the epigrams about immobility and irreparability, with their soft falls of a third, in some sense reproduce the sound-tint of these very words. In this opera, even more than Otello, Verdi comes closest to realizing the old dream of the inventors of opera, a tragedy in which speech rises effortlessly, imperceptibly, into song. When Verdi in 1875 compared his achievement to Wagner's, he noted, “I, too, have attempted the fusion of music and drama … and that in Macbeth”; Verdi hadn't yet written Otello or Falstaff, but in those late operas he approached Shakespeare through the highly wrought, semi-opaque medium of Boito's poetry and dramaturgy, whereas Piave provided a fairly clear image of the original Jacobean text.

Verdi's great achievement in this liminal area far beneath bel canto, where singers make whispery harsh sounds, is the grand duet Fatal mia donna!—an astonishing psychological study of the tremors of spiritual remorse combined with the hilarity of gratified ambition (see ex. 31).