By the way, you can watch this video while analyzing this fugue. This will help you to understand it's structure even better.
The subject of this fugue is built from an ascending pentachord (5 scale degrees) with chromatic notes inserted between the 3rd, 4th and 5th scale degrees in 3/4 meter. This arrangement is very common in the Baroque music.
The fugue begins with the subject in the soprano (E minor, tonic) after which follows an answer in the alto (B minor, dominant, measure 8). In measure 16, the subject enters in the tenor (E minor, tonic) and the answer in the bass (B minor, dominant, measure 20). The cadential hemiola in measures 26-27 concludes the exposition.
The episode connecting exposition with the elements of counter-exposition in measures 28-31 is based on the chromatic ascending line of the subject. Here tenor and alto voices move in canon.
Full subject entries don't appear after exposition. The composer seems to like to develop only the ascending or descending chromatic line. It starts in measure 32 where the subject material enters in the bass (E minor, tonic). Then from measure 38 follows 3 descending chromatic lines (subject in inversion). First in the bass (E minor, tonic), then twice in the soprano (measures 45 and 48).
In measures 54 and 58, there are ascending subjects in the bass part (A minor, subdominant and E minor, tonic). The fugue concludes with a hemiola and a meter change (to 3/2) at the end.
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