Johann Sebastian Bach’s Fugue 16 in G Minor is an example of a conventional fugue. What is interesting about this piece is that the body of the fugue is comprised of fragments of the subject and countersubject. The material within the episodes are a unique to this fugue. Also, inversions are found in key spots within the piece, and also create a similarity between the answer and countersubject.
Within the first 3 measures, you find Bach brilliantly transcripts the first part of the answer and positions it at the end of the countersubject in an inversion. You also find that there is an inversion between the beginning of the countersubject and the end of the answer. Something similar, using this technique, arises at M. 24 in the alto and soprano voice. The ascending D, E-natural, F-sharp, and G sixteenth note figure is found in an inversion, a descending D, C, B-flat, and A figure, leading into an episode.
Normally, episodes do not contain any subject matter, but Bach cleverly placed fragments of the subject and countersubject to aid in modulating to the next closely related key. Measures 8-11, episode one, the fragment(s) are heard throughout every count in different voices, modulating to the relative major of B-flat.; this, as well, occurs in episode two. Episode three, occurring in mm. 24-27, is, to some extent, contrastive to the rest of the piece. Here, tonicization back to the home key takes place, while the bass voice begins to mimic a kind of augmentation. The first note of every eighth two sixteenth figure, in order, outlines the subject of the fugue. Together, these two compositional techniques successfully modulated back to the home key of G Minor.
In essence, whether it be the episodes modulating to a new key, or tonicizing back to G Minor, the entire fugue comes solely from the subject. Bach achieves this by using fragments of the subject, inversions, tonicization, and augmentation. With these...