Melodic InversionPlease continue this section by inserting the Inventionen & Sinfonien disk in the CD-ROM drive and following the textural animation of Bach's Two-Part Invention in C Major. (Click the "Back" button at the top left of the browser to return to here.) The animation shows that, like Contrapunctus the Clown, Bach's Invention is a musical circus, of sorts, in which melodies are turned over and repositioned in relation to each other. Observe that the hot colors represent the invention's original motive while the cool colors represent melodic inversions.
You should be familiar with "melodic inversion" from our study of canon last week. Recall that the follower of a canon in contrary motion moves its intervals in the opposite direction of the leader. In other words, the follower is the "melodic inversion" of the leader. But melodic inversion happens in all kinds of music, not just canons.
A motive (single object) is melodically inverted when its intervals move in the opposite direction to a prior motive. It is not a requirement that intervals retain the precise quality of the original. For example, a rising major 3rd in the original might become a falling minor 3rd in the melodic inversion. However, in instances where the precise quality is maintained, the derived motive is said to be the "mirror inversion" (see mirror canon). Composers often invert melodic contours without adhering even to the basic number of the interval. For example, an ascending fourth might become a descending sixth. While related to "melodic inversion," such treatment should properly be called, depending on the degree to which the composer has taken liberty with the basic intervals, "contour inversion" or "imitation."
The following examples of melodic inversion are from Bach's Two- and Three-Part Inventions. Compare the direction and size of intervals in the melodic inversions to those of the original motives. Do you hear any examples of mirror inversion? Contour inversion?
Two-Part Invention No. 14 in B-Flat: The motive of this invention divides neatly into two halves--the second half is the melodic inversion of the first.
In mm. 4-5 Bach gives the first half of the motive to the left hand and the second half (the melodic inversion) to the right hand.
Three-Part Invention No. 1 in C: This invention begins with a rising scale figure in the highest voice. In m. 4 the motive is appears, melodically inverted, in the bass voice.
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©1996 Timothy A. Smith
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