The Art of Fugue
We might be excused for needing slightly lighter fare after the massive Contrapunctus VIII, so here it is. As the name double fugue implies, this one has two subjects, and here they are.
The second one is just the main AOF subject, augmented from its incarnation in Contrapunctus I. The new first subject, which opens the fugue, is a long, flighty line that zips around the voices throughout the fugue, giving it a perpetuum mobile character.
The juxtaposition of the main AOF theme with its much lighter foil somehow changes its character, in that wonderful Bachian way, from its somber nature in the early fugues. Now it sits in the different voices like a solid presence — almost an elder statesman after some forty minutes of music-making — underpinning the exuberant youngster dashing all around it.
You’ll also hear another marvelous example of double counterpoint in this fugue, as in the Canon alla Decima. For example, the first time the two subjects appear together, they’re both on D, with the AOF subject in the soprano (listen for it at 0:40), but later they appear with the AOF subject on D in the bass, and the flighty subject on A in the soprano (1:46). This example of double counterpoint at the twelfth prepares the ear for the counterpoint to come in the Canon alla Duodecima.