Lorenzo and Jessica enjoy music and singing on the moonlit Belmont estate at the beginning of Act III. The romantic and peaceful environment is highlighted by their conversation and love duet, which highlights the play's humorous and lighter tone.
When Shylock arrives in Belmont seeking vengeance for the humiliation and financial losses he suffered in Venice, the mood changes. Jessica hears her father approach, and she and Lorenzo flee, leaving the music unattended. The music that once symbolized joy and love becomes a source of irony and foreshadowing as Shylock's dark presence disrupts the Belmont idyll.
The music takes center stage in Act IV when Portia and Nerissa, disguised as Balthazar and a law clerk, arrive in Venice. Portia's eloquence and wisdom as she defends Antonio in the courtroom are enhanced by the presence of music. When Portia presents her argument that Shylock should show mercy, she invokes the divine power of music, and her speech becomes a kind of musical performance. She appeals to the court and the audience's sense of harmony, peace, and compassion, which resonates with the themes of justice and forgiveness.
The music plays a significant role in Act III and IV of The Merchant of Venice, underscoring the emotional states of the characters, enhancing dramatic tension, and adding depth to the play's themes of love, justice, and the power of persuasion.