How do episodes connect statements of the subject in a fugue?

In a fugue, episodes serve as connective melodic passages that separate the various statements of the subject. While the exposition establishes the subject through successive entries in the constituent voices, the subsequent structure of the piece often relies on these episodes to provide variety and transition between restatements of the subject.1

During these episodes, the subject typically appears only fragmentarily, if at all, allowing the music to move between different tonal centers or to explore different treatments of the thematic material. Episodes are often characterized by a reduction in the number of active voices; it is common for an episode to proceed in as few as two parts, even in fugues written for three or four voices. By alternating these connective passages with the more formal statements of the subject, composers can manage the unfolding of the fugue and determine its overall duration and complexity.12