Bach: WTC I, Prelude and Fugue in D major

In this prelude and fugue, at three minutes long shorter than your typical pop song, Bach shows us yet more ways to write a prelude and fugue. The prelude is another moto perpetuo like the C minor prelude, but this one is done differently, with scale passages over a secco bass line. There is a brief fantasia-like passage at the end leading to the cadence. The two big chords are interesting: the first one is viiº7 of I and the second is viiº4/3 of V. Then V-I. I remembered one theory professor saying quite casually that EVERY piece in the common practice period ends with either a V-I cadence or a  IV-I cadence. But if I recall correctly there may be a Bach chorale or two that ends with an odd cadence. 

The fugue subject is nothing more than a variant of a standard Baroque ornament followed by a brief scale passage. What makes it exciting is the rhythmic verve. We haven't talked about this, but Bach's subjects all tend to be rhythmically really appealing. Here is that subject:

And here is where I think it came from. First of all, from the guide to ornaments found in the introduction to an edition of the WTC. As you can see, six of the notes are the same:

This is the double cadence, from Rameau's table of ornaments:

Bach's group of eight notes is a bit different from either, of course, but I see a family resemblance. It you were sitting at the keyboard, just fooling with these ornaments, you might stumble across what Bach uses here. Rhythmically it resembles the double cadence and the trill from below, but he has organized the notes to, instead of functioning in a cadential context, to simply suggest a tonic triad on D. He follows this with nothing more than a scale segment in dotted notes. And that's it. A fugue subject that, while it sounds complicated because of the 32nd notes, is actually very bare bones.

The fugue is quite brief, only 28 measures, but there is room for lots of sequences. Here is an ascending fourth sequence:

And he soon follows that with a sequence descending by step. Because of the nature of the subject, sometimes he is doing a stretto that you might mistake for just another sequence, as in m. 13. And sometimes he does a stretto between outer voices and stuffs a false entry in the middle as in m. 20. At the very end, just preceding the cadence, he doubles the ornament motif in tenths for two measures and follows that with the dotted motif in filled out chords for two measures. Cadence, done. Another example of Bach doing a great deal with very little.

Here is Friedrich Gulda with the D major Prelude and Fugue: