|Book 2 - No. 23 - B major - Fugue|
The subject of this fugue is curiously simple. It climbs one complete octave from B to B. It moves in stately half-notes across four measures and falls into four gestures: up, down, up, up-down. The final gesture starts on the tonic (B) where the subject is essentially completed but subsequently falls downward in faster notes beginning the inevitable momentum into counterpoint. The four gestures outline a bold but simple harmonic progression of I-IV-V-I , one measure to each chord. Notice also that the subject uses 7 scale tones, omitting only the 5th degree of the scale which is implied by the dominant harmony in the 3rd measure. The simplicity and the completeness of the subject combine into an effect of absolute, eternal solidity.
As in most fugues, the formal design exhibits a clear sectional organization, in this case, into four sections. It is much like a little play in four acts. Each of the four sections includes two features which define its boundaries. First, each section ends in a strong cadence, a stable confirmation of tonality (key) that acts much like a period in a sentence. Second, each of the sections begins with a thin texture, a small number of voices, that generally grows throughout the section (the third section thins again at the end, preparing for the final section). This is natural at the beginning of any fugue; the exposition is a mandated growth in texture from one to the maximum number of voices. But here, each of the subsequent sections begins with a notable absence of one or more voices. Within each section, the texture grows, shrinks and grows again and voices come and go.
In addition to the sectional organization, there feels to be a larger, overarching development to the fugue as a whole. It is based largely on this iterative growth in texture, cyclically reinforced by the four sections, each being a nested example of the same phenomenon in miniature.. It is perhaps surprising that over time, the subject entries become fewer and spaced farther apart by intervening episodes. This is not unusual in fugues. Here, it supports the feeling that the texture and content of the fugue grows or develops, and that what is growing is the surrounding context of the subject, not the subject itself. It illustrates how by becoming less frequent, subsequent subject entries become more profound. The more we expect it, the more rare it becomes. And thus, the more meaningful it is, when the subject finally appears again.
The second section introduces a prominent countersubject which is regarded by some as a second subject. They consider this to be a double fugue. In this case, it would be an example of a double fugue where the second subject is exposed as counterpoint to the first, never independently. Yet the supposed second subject is degenerate in two ways. First, it is never given a complete exposition comprising all four voices of the texture. Second, as a subject, it is musically weak. As counterpoint to the first subject, however, it is marvelous. As Altschuler points out, it is built of 8th note steps, perfectly contrasting the 1/2 note leaps of the original subject.