What is the structure of music made up of two sections that may be repeated?

The correct structure, which comprises two sections that can be repeated, is often represented as AB. In this structure, "A" denotes the first section of the music, and "B" signifies a contrasting section that follows. When performing music in this AB format, the A section can be played again after the B section, resulting in a repeating pattern of A and B. This basic form is common in various musical styles and provides a straightforward and clear way to organize musical ideas.

In contrast, the structures represented by the other options differ in their organization. The ABA structure includes a return to the first section after the contrasting B section, which creates a sense of fullness but also adds complexity. The AA structure indicates two identical sections without any contrast, leading to a uniform sound throughout. Finally, the ABC structure introduces a third section that adds more diversity but does not align with the requirement for just two sections. Therefore, the AB structure is the appropriate choice for the definition provided.