Passage: In western classical music, composers often introduce an initial melody, or theme, and then create variations. Classical music often has several melodic layers, called polyphony, such as those in a fugue, a type of counterpoint. Often, melodies are constructed from motifs or short melodic fragments, such as the opening of Beethoven's Fifth Symphony. Richard Wagner popularized the concept of a leitmotif: a motif or melody associated with a certain idea, person or place.

Question: What idea did Richard Wagner make popular?
leitmotif