Which term describes a recurrent theme developed throughout a composition and represents "the beloved" in Berlioz's work?

The term that describes a recurrent theme representing "the beloved" in Berlioz's work is "idée fixe." This concept is particularly significant in Berlioz's composition "Symphonie Fantastique," where the idée fixe serves as a unifying thread throughout the various movements. It embodies the protagonist's obsessive love for a woman and reappears in various forms, reflecting the character's emotional states and narrative developments. The idea of a fixed idea in the music allows listeners to recognize its transformations and the evolution of the protagonist's feelings, which adds depth to the overall composition.

Other terms, while relevant to musical structure, do not convey the same specific meaning as idée fixe. Melodic themes can be broader and may not necessarily represent a specific narrative or emotional concept. A motif usually refers to a short musical idea that might not be as developed as an idée fixe, and a counter-melody is a complementary line that supports the main melody rather than serving as a symbol or representation of a thematic idea.