In Act 3, Scene 5, the Duchess uses alliteration to convey her perception of her brother’s immorality and deceptive behavior. The Duchess has just received a letter from Lord Ferdinand, and Bosola describes its content to her. Her brother has sent along wishes of love and safety. However, the Duchess understands that Ferdinand does not actually wish her well and is in fact responsible for a great deal of danger coming to her and her husband Antonio. Therefore, she does not trust the letter that Bosola has brought. She highlights her distrust by using alliteration, saying:
Thou doest blanch mischief;
Would'st make it white. See, see, like no calm weather
At sea, before a tempest, false hearts speak fair
To those they intend most mischief.
In her speech, the Duchess uses the repeated /f/ sound in a phrase that questions her brothers’ intentions ("false hearts speak fair"). She believes that their ploy of kindness will only lead to greater violence. Their deception, and her ability to pick up on it, is accentuated by this instance of alliteration. The rhythm and movement of her lines makes her seem wise, and her use of repeated sound highlights the duality in her brothers’ behavior. She calls out her brothers’ deception, referring to how their "false hearts" in their loving message ultimately conceal their true intentions; and the audience pays special attention to this moment because of the alliteration. The Duchess hasn’t missed the trick, and the audience is made aware of it in this moment.
In Act 4, Scene 2, a madman enters and sings a song that seems to encapsulate the play’s trajectory of violence and darkness. The madman’s lyrics are rife with alliteration and description, and his song creates a moment of tense anticipation and reflection for the audience. This scene precedes the death of the Duchess and her children, so this external character and bard needs to thematically introduce the scenes of great violence that will follow. He sings:
Oh, let us howl some heavy note,
Some deadly dogged howl,
Sounding as from the threat’ning throat of beasts and fatal fowl,
As ravens, screech-owls, bulls and bears!
The madman’s song is pulled along by melody and imagery, but its lines also contain a great deal of alliteration. The purpose of this alliteration (especially the repetition of the /h/, /d/, /th/, and /f/ sounds) is to accentuate the madman’s descriptions. It does so by highlighting the rhythm of the language, which is especially important in sung form. The frightening beasts that the madman describes come to life through the sounds of his language. The alliteration in his song often comes in paired phrases; two words after one another that begin with the same letter, as though the words themselves are advancing in groups of two: "deadly dogged," "threat’ning throat," "fatal fowl." This pattern of alliteration continues in the last line in the repetition of the /b/ sound ("bulls and bears!"). The madman’s ability to create a heavy mood is hinged on the eerie cadence of his singing and the strange pattern and rhythm of the lyrics themselves. This rhythm comes from the alliteration that animates the song’s frightening imagery.
