|Book 1 - No. 20 - A minor - Fugue|
A long subject, a long composition, and despite several sprinkles of episode, this fugue is utterly saturated with the subject and its mirror image, its inversion. The design of the fugue has 39 subject entries ranking with Book 2 No.3 in C-sharp-major in terms of the largest number of subject entries in the entire Well-Tempered Clavier. To create variety and narrative, Bach first partitions the subject entries essentially in half: 50% of the subject entries are inverted. The subject and its inversion are then juxtaposed between and within sections. Given equal independent treatment, the subject and the inverted subject each have their own exposition, and their own "development" sections using stretto. These four sections are interleaved to alternate between subject and inversion. The final two sections interleave pairs (each pair joined in stretto) of subject and inversion in a final tension-filled debate. The alternating juxtaposition accelerates until each pair has only time for partial subject statements, subject and inversion inextricably tangled, compressed, ultimately exhausting each other in a dramatic end. Perhaps the whole fugue can be encapsulated by a metaphor: matter and anti-matter come together until they cancel each other into non-existence.
Altschuler and Bruhn differ in their tally of subject entries (including inversion) by 2. Bruhn has 39/19, Altschuler states 37/17. There are two, probably incomplete, inverted subject entries that Bruhn counts and Altschuler does not. Both provide excellent analyses with explicit accounts of each entry. While the difference is likely a hairsplitting academic debate, it is interesting to note this dispute. Are you willing to try counting with only your ears? What a great opportunity for careful listening. In the end, the exact number is not the point. But how interesting that Bach's dense counterpoint often results in a very tough nut to crack: a jewel whose surface is difficult to scratch.