Bach: WTC, Bk I, Prelude and Fugue in A major

The prelude to this delightful pair has more invertible counterpoint than most fugues. In that sense it rather resembles some of the two-part inventions that Bach used to demonstrate how to use invertible counterpoint. When I refer to "invertible counterpoint" I mean the kind where one voice is transposed an octave below (or above) the other voice which flips all the intervals: thirds become sixths, seconds become sevenths and fifths become fourths, which is the tricky part as the fifth is a perfectly consonant interval, but fourths often have to be resolved.

Here is the subject and its accompaniment (I have removed the extraneous voices):

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That's a nice charming, simple theme that starts and ends on A. In the very next measure he gives us the same pair, but this time on E and he puts the sixteenth-note theme in the bass and the quarter note bass line in the alto. Then he has a five measure episode developing a theme in thirds in the soprano and alto in eighth notes.  Then he has the original pair again, slightly varied, but this time starting on F# and with the original order of the sixteenths on top and the quarters on the bottom. This ends with a cadence in F# minor. Another couple of measures of episode develops the eighth-note theme in a different way followed by the original pair on A, but with the sixteenth-note theme in the bass and the quarters in the alto with a soprano free variation above. This is followed by the original theme and accompaniment, in A again, and in the original orientation. Two measures of scales, cadence and the piece is over. It is a veritable compendium of invertible counterpoint and it is just barely over a minute in duration. The fugue is simple in comparison.

The oddest thing about the fugue is the weird rhythmic configuration of the subject. Here is the subject and the answer with the other voices left out:

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He often develops the middle five notes of the subject, leaving out the first rhythmically isolated note, but apart from that, the fugue unfolds in a fairly usual fashion except the second half is decorated by running sixteenths. Here is Sviatoslav Richter and the score: