Bach: WTC I, Prelude and Fugue in G# minor

Wow, it has been two weeks since I last posted a Bach prelude and fugue. I guess I was busy or something. I do want to finish Book One of the Well-Tempered Clavier because I have a new project in mind. I haven't been paying much attention to Bartók in recent years and I feel it is time to rectify that. So, as soon as I finish the Bach project you are going to see a lot of Bartók.

But first, on to the prelude and fugue. This polyphonic pair is characterized by, among other things, invertible counterpoint. I have written about this in the past, but this provides an occasion to review. Invertible counterpoint occurs when you take the upper voice and make it the lower voice and vice versa. This is feasible for most intervals, minor thirds become major sixths and seconds become sevenths, for example, though you do have to watch how you resolve dissonant intervals. But the problem is fifths, a perfectly consonant interval which become fourths, an often dissonant interval requiring resolution. So there you go, just avoid fifths. Easier said than done, of course. Here are the first two measures of the G# minor prelude showing how it is done:

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As you can see, the upper voice melody in measure one becomes the bass in measure two. The bass in measure one becomes, an eight-note delayed, the highest voice in measure two and the inner voice migrates up an octave to become the alto. Easy as really difficult pie as Willow would say. No, it's not so difficult, but you will notice that Bach avoids fifths here. There follows a series of sequences ending with a cadence on the sub-dominant, C#. More modulatory sequences take us in the direction of the sub-dominant of the sub-dominant, i.e. F#. A lot of the prelude is simply development, in different harmonic contexts, of that little sixteenth note motif we hear at the beginning. This leads to a lovely descending fifths sequence from measure 19 to 22:

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Oops, sorry, I omitted the sharp after the A, it should be A# to D#. After a bit more playing around with the basic motif, we have a leisurely cadence with a tierce de Picardie and Bach has taught his sons, and us, how to do invertible counterpoint and sequence. Not bad for a prelude lasting just over one minute.

The fugue is a very organic one with no fancy counterpoint. But it is all about the subject and two motifs from it that are developed in five different episodes. Here is that subject with the motifs shown:

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There are two interesting motifs in this short subject and Bach develops both of them. The basic layout of the fugue is entry of all four voices in subject-answer pairs (tonal answer) followed by an episode on motif B, which is often accompanied by secco chords. Then there is a solitary answer followed by another episode on motif B. we have a pair of entries, subject and answer with a new episode, this time on motif A. A couple of odd entries follow: the subject on D# (real) and then on F# (tonal). There is a final entry of the subject, on G# followed by another episode on motif B and the final cadence.

This fugue is all about deconstructing the subject and developing the resulting motifs. No strettos, no augmentation, just that subject and what Bach does with it.

Here is Sviatoslav Richter and the score: