The heading “Fantasy”, the use of triplets and the rather impetuous nature of the piece, this very case-sensitive style …
This style was more common in the works of the sons of Bach: episodes with crossing arms on the keyboard were regularly featured in the works of both Karl Philip and Wilhelm Friedemann. They often experimented at home …
A fugue is a completely different matter. While the chromatism in Fantasia was more about ornamentation of the melody, here it fits into the very strict boundaries inherent in the fugue. Bach constantly uses unusual reduced intervals and augmented chords, often using dissonances on purpose. It turns into a kind of a kind of harmonic distorting mirror – as if an ordinary fugue begins to “roll down a slope” …
But at one point everything changes! Fast passages seem to return from nowhere, led by a new theme. You can also see the crosshairs of the hands, but in general the technique meets the standards of the Bach fugue.
And only the theme of the chromatic fugue returns – Bach, it seems, decides to clarify some points: the manuscript breaks off right in the middle of the page, leaving us in a somewhat puzzled state face to face with the musical “question mark” at last …