If you listen to the G-sharp minor from Book I of The Well-Tempered Clavier, you will find commonalities with the G-sharp minor from Book II. This key is by no means optimistic; it can certainly be understood as an expression of sorrow. In this fugue, in particular, this is expressed through long phrases, and the degree of sorrow deepens as the piece progresses.

Furthermore, Bach expresses sorrow by employing chromatic progressions, which were considered taboo during this era. Chromatic progressions are found throughout this fugue. The theme appears 11 times in this fugue, and the final statement of the theme proceeds in perfect alignment with this chromatic progression.

Let's consider the theme from measure 1, spanning measures 1-4. Measures 1-2 and 3-4 form an ascending sequence, but the tension of sorrow is considered to increase further in measures 3-4 compared to measures 1-2.

Upon reaching measure 5, the alto begins the theme, at which point the soprano proceeds with a chromatic progression, deepening the expression of sorrow even further than before. This is how the piece progresses.

All appearances of the theme, except for the E major statement in measure 111, are in G-sharp minor or D-sharp minor. This E major theme might be the only theme that conveys a sense of calm. As the piece approaches its end, the sorrow of the theme intensifies even further.

While it was mentioned that the theme in measure 5 is accompanied by a chromatic progression, where only three notes (in this case, B, B-sharp, C-sharp) within the range of a major second ascend or descend, the chromatic progression accompanying the theme in measure 125 involves six notes (in this case, G-sharp, F-double-sharp, F-sharp, E-sharp, E, D-sharp) within the range of a perfect fourth, indicating an expanded range and intensified emotion. This is a suitable place to increase the volume.