Many specialized techniques can enter into the imitative polyphony of fugues, and the art of composing them has been so often analyzed and taught in the wake of Bach that a whole terminology has grown up. In addition to exposition, subject, and episode, there is the countersubject, a kind of second subject that fits together in counterpoint with the first, shadowing it in all its appearances after the beginning.

Composers may lengthen or shorten all the notes in the subject, making it twice as slow or twice as fast. They might turn the melody of the subject upside down, inverting its every interval (so that where the original subject went up a step, the inversion will go down, and so forth). Very often they shorten the space between subject entries from what was heard in the exposition, so that the entries follow one another faster and are stacked almost on top of each other. This technique is called stretto (the Italian word for “narrow”). All these possibilities and more are basic to the ingenious contrapuntal art of the fugue.