The Art of Fugue
We’ve seen how we can take the subject from Contrapunctus V:
and divide its note values by two to get a diminished copy of the subject in Contrapunctus VI:
If we can divide, why not multiply by 2, to get an augmented version of the subject? That’s just what Bach does here, to get this.
This is a 2X copy of the top subject, and 4X of the diminished subject, as you’d expect. And — incredibly — Bach manages to superpose all three of these and their inversions in a magnificent fugue in which the augmented subject marches inexorably upward through the voices. You’ll hear its long, sonorous notes singing forth at 0:10, 0:58, 1:29, and 2:07 in the bass, tenor, alto, and soprano, respectively, and by the time the alto entrance arrives, this formerly lighthearted fugue is rolling along like a juggernaut, leading to a splendid five-voice finale that wraps up the set of stretto fugues in fine style.