Despite its short rondo theme of just over four measures and concise two-voice texture, it is a relatively long work, exceeding 130 measures. The title "Fantasia," while conventionally referring to contrapuntal content at the time, here seems to further signify the power of imagination that created unexpected combinations. What Bach attempted here was the combination of rondo form and contrapuntal writing. The fundamental difficulties arising from this combination lie in the fact that the various voices, which should ideally continue horizontally with equal weight, are, so to speak, interrupted by the recurring theme; and furthermore, the rondo theme and the contrapuntal themes of the episodes compete, diminishing each other's effectiveness.

Frankly speaking, it is difficult to say that these challenges are fully resolved within the work. While each section certainly flows seamlessly, this implies that the return of the theme is not prepared with a sense of tension. The episodes begin with imitation but eventually develop using material from the rondo theme, blurring the contrast between the couplets (recurring sections) and the episodes. There is also a lack of variation in range and tempo, making it difficult to immediately identify climaxes within the overall piece. For both performer and listener to fully appreciate it, detailed analysis would likely be necessary.

The rondo theme appears approximately three more times in addition to the beginning of the piece: at measure 29, measure 80, and measure 120. This rondo theme has a further eight-measure continuation. In the first episode (measures 13-27), the latter half of the rondo theme appears almost not at all. Furthermore, the second episode (from measure 33 onwards) begins with invertible counterpoint of a seemingly unrelated motive. However, the quarter-note syncopated motive that dominates most of this section is derived from the latter half of the rondo theme. The third couplet at measure 80 is expanded by the inversion of the first two measures of the rondo theme (a contrapuntal technique of interchanging upper and lower voices). The subsequent episode also repeats the two-measure inversion used in the couplet, but its content consists of motives derived from the latter half of the rondo theme and the second episode. The strict inversion temporarily concludes at measure 99, but thereafter, short one-measure inversions and similar paraphrases are interspersed. Then, from measure 116, a dotted rhythm, previously heard only briefly at the conclusion of the first half of the rondo theme, appears in the left hand for two measures, hinting that the piece is nearing its end. The range of both hands expands, a long trill is placed in the left hand, preparing for the final presentation of the rondo theme. This completes the latter half of the rondo theme and perfectly matches its initial presentation.

Viewed in this way, it becomes clear that Bach meticulously advances the presentation and development of the theme beneath the surface of the rondo form, where couplets and episodes alternate.

Furthermore, the smoothly flowing two parts reflect an awareness of the galant style, which was the latest trend at the time. It can be said that this work emerged from Bach's ambitious incorporation of new forms and styles into his own established domain.