On the Wikipedia page on BWV 578, a technique devised by Corelli is mentioned.

The fugue's four-and-a-half measure subject is one of Bach's most recognizable tunes. The fugue is in four voices. During the episodes, Bach uses one of Arcangelo Corelli's most famous techniques: imitation between two voices on an eighth note upbeat figure that first leaps up a fourth and then falls back down one step at a time. (em mine)

I can't understand the last sentence. I somewhat understand the last bit about the fourth, but the part about imitation is a bit beyond me. Could someone rephrase that part in simpler language and explain it?


Luke, part of the cause for your confusion stems from the poor grammar in the Wikipedia article. I actually had to read the highlighted excerpt twice to make sure that I understood it correctly.

A fugue, begins with what is called a subject, an identifiable motive or phrase that serves as a calling card for the piece - drawing the listener's attention during highly complex parts and creating cohesion throughout a piece.

After the subject is stated, it is followed by what is called an answer in another voice. An answer may be done through imitation, which means exactly as it sounds (think "monkey see / monkey do").

A fugue cannot continue until all of the voices have entered the music (much like the way you would spin tops consecutively and watch them all spin.)

The last sentence that you highlighted indicates a phrase that ascend by the interval of a perfect-fourth and then descends by step back downward to the original pitch.

A musical example of this would be jumping upward from C -> F, and then "falling" (descending by step) back down to C: F -> E -> D -> C

Regarding the "eighth note" comment, the author could have meant one of two things:

  1. That the ascending / descending figure only occurs on a succession of upbeats.
  2. That the ascending / descending figure begins on an off beat with an eighth note rhythm.

It is hard to say without context of looking at the score with the specific measure numbers.

I would also like to add that the Wikipedia article cited is quite, quite flimsy, and a very poor representation of analysis for one of Bach's most famous fugues. I would highly suggest looking into other materials if you are in fact interested in learning more about the work.

Hope that helps.


Imitation is when a voice directly repeats an idea that was just stated in another voice. It does not have to start on the same not. So in this case, imagine two parts that take turns playing a fourth up and steps going down.

Imitation is closely related to sequences, which is when you repeat a melodic fragment several times, usually going up or down a scale. ex. (CFED)(DGFE)(EAGF)

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