The Mouth of Sauron is the forty-third soundtrack of the Complete Recordings of The Lord of the Rings: The Return of the King.
It plays as the Mouth of Sauron brings the false message of Frodo's death to Gandalf, Gimli, Pippin and Merry, and as he is beheaded by Aragorn.
It also plays afterward during Aragorn's speech to the combined forces of Gondor and Rohan at the Black Gate and as Sam carries Frodo up Mount Doom.