The Art of Fugue
This canon employs a complicated variation of the AOF subject that you will hear, as usual, stated at the outset and then followed after eight measures by a voice a twelfth (“duodecima”) higher.
The structure of this canon is similar to that of the canon at the tenth.
It employs double counterpoint, with the second instance of the canon again at the octave.
You may notice a steady progression in the nature of the AOF canons. First, we heard a canon at the octave. Then came a canon at the tenth. It’s hardly surprising that this one raises the interval an analogous amount to the twelfth. This kind of methodical progression is on display in even more detail in the Goldberg Variations.