In a fugue, what do the blue lines represent?

In a fugue, the blue lines represent subjects. The subject is the main theme or melody that is introduced at the beginning of the piece and is then developed throughout by various musical voices or parts that enter sequentially. Each entry of the subject is typically imitated in different pitches and may be manipulated through various contrapuntal techniques.

Fugues often feature the subject prominently as it serves as the foundation for the work’s structure, guiding the listener through the composition as it interweaves with counterpoints and develops in complexity. The term "subject" in the context of a fugue specifically refers to this primary melodic material, which contrasts with the other terms in the answer choices. Counterpoints refer to the melodic lines that accompany the subject, melodic variations suggest alterations of a theme rather than its foundational representation, and chorales are typically associated with hymn-like settings rather than the specific structural components of a fugue. Thus, recognizing the blue lines as depicting subjects provides insight into the essential elements of counterpoint in fugue writing.