When J. S. Bach was around 28 years old he put this canon in the album of his cousin Johann Gottfried Walther, a versatile composer in his own right, as were many in the Bach family. Bach and Walther's friendship was strengthened during Bach's time in Weimar where Walther was the town organist, and the canon, dated 1713 is from the middle of Bach's time there. *
Walther was fond of writing canons as well, and Bach's solution to Walther's canon was featured on this site as our Feburary 2018 puzzler. Instead of looking further at Walther's canon, let's look at the one that Bach wrote for Walther.
Bach's canon is composed in four voices at the fifth, and shows a methodical and stragetic approach. It is a 'stacked' canon, meaning that the same pitch and rhythm interval of imitation occurs between all adjacent voices; in this case each interval enters a half-note after and a fifth higher than the previous voice. **
Style
The canon clearly fits into the renaissance tradition of canon. Just listening reveals the kind of harmonic motion that is antiquated. Yet Bach takes advantage of his craft, using accented passing ttones, occasionally allowing richer harmonies to result. There is a much higher focus on harmonic sense than harmonic gravity. Because of the canonic structure's quick succession of entries and lack of rest, one hears close imitation peeking through the texture as a result of constant stepwise motion drawing the attention to changes in direction.
Composition
Bach so effectively uses contrary motion, not in the sense that imitation occurs by contrary motion, but rather in the sense that the leader changes direction just as the follower begins to follow, resulting in cascading counterpoint between the voices.
Bach succeeds at creating this listening experience by adhering strictly to conjunct motion. While this is a mark of well-formed melodies, here it is extreme: except for a few distinct places all motion is by step. This helps ensure that no dissonance goes unresolved. It also helps to form the intricate texture: with four busy voices running constantly.
* many sources relate these events: Wikipedia "J.S. Bach"; The New Grove "J.S. Bach"; C. Wolff's book: Bach: The Learned Musician, etc.
** Articles by Gosman and Collins on stacked canons:
Collins, Denis. 2002. “Bach’s Occasional Canon BWV 1073 and ‘Stacked’ Canonic Procedure in the Eighteenth Century.” BACH 33 (2): 15–34.
Gosman, Alan. 1997. “Stacked Canon and Renaissance Compositional Procedure.” Journal of Music Theory 41 (2): 289–317. https://doi.org/10.2307/843961.
Both of these articles are highly recommended to anyone wishing to learn more about the structure and compositional practice of writing stacked canons.