Bach: WTC I, Prelude and Fugue in C# major

This prelude reminds us that Bach intended the Well-Tempered Clavier as a teaching resource for his children, three of whom became leading composers in the next generation, so I guess that worked! Much of the prelude is a demonstration of invertible counterpoint as the opening eight measure phrase is immediately followed by another in which the voices are inverted. Then another where they are inverted again. And another! This is then fragmented into shorter phrases, again alternating with their inversions. Two thirds of the prelude consists of these demonstrations of invertible counterpoint. I don't want to get into all the details here, but have a look at my post on the mirror fugues from the Art of Fugue for some more discussion of inversion.

Once the long section in invertible counterpoint is done, Bach turns to sequence and modulation for the last part of the prelude. Again, you should notice that the structure and resources of this prelude are completely different from the ones used in the first and second preludes. Incidentally, I forgot to include the score in yesterday's post. You can always go to IMSLP for any of these scores. The Well-Tempered Clavier is here. Here is the prelude:

The fugue, in three voices, has a subject that easily divides into two parts:

The first part, with a little turn, outlines the tonic triad while the second, leaping up in sixths, has a cadential feel. Once the three voices have entered with the subject the first episode, beginning in m. 7 uses an inversion of the turn to accompany a little motif derived from the falling triad outline. Then the turn is turned right side up and we get another statement of the subject in the dominant, G# major. The episode uses that decorated triad motif, but this time inverted. The next statement of the subject is in A# minor and is followed by an episode based on the turn figure in various forms. The next statement is on E# minor and so on. The whole fugue is very tightly focused on the material of that subject and the countersubject is in very neutral running scale passages in sixteenths--which you could argue is just a version of the turn figure. The developmental episodes, working out all the possibilities of that subject, dominate the fugue which has no strettos and not that many statements of the subject. The second page only has the subject five times. I won't put up the score to the fugue as I found a YouTube clip that includes it. Here is Sviatoslav Richter with the Prelude and Fugue in C# major: