In a fugue, what is an "episode"?

In a fugue, an "episode" refers to sections that provide a departure from the main theme, or subject, allowing for more free-form exploration without presenting the subject in its entirety. During these episodes, the music often develops using motifs derived from the subject, creating a contrast to the structurally rigid presentations of the subject that occur in other parts of the fugue.

These episodes serve to expand the musical ideas and create a sense of development, maintaining interest and cohesion before returning to the subject again. They are crucial to the structure of a fugue, as they help to build complexity and transition smoothly between different thematic material while still relating back to the main subject of the composition.