The Prelude is made up of only two themes, one associated with Aida and the other associated with the priests. Aida has two loves, love for Radames and the love for her country/family. In Act I she prays to the gods for the safety of her father, then recalls what victory would mean for Radames when he goes to war with Ethiopia and its king, Aida's father. In Act II she sings the definitive statement of her own theme (see below).
The priests entrust the fate of the holy land that is Egypt to the gods, give thanks to the gods for victory, and finally declare Radamas a traitor. Ramfis declares: "You violated your oath, false to your country, your King, your honor." The music associated with the priests is usually treated as counterpoint.
The Prelude, with its two themes, perfectly sets the stage for the dialogue that begins the opera, and suggests that the gods will play a role in its conclusion.
The video is a performance of the NBC Symphony, Arturo Toscanini, conductor.