Invention: Exposition

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For our purposes in this class, we will call the first section of the piece, where the motive-countermotive pair appear 2, 3, or even 4 times in close succession, the exposition. These multiple appearances of the motive-countermotive may all appear with the same harmonic support, starting on the same pitch-name though in different octaves (Inventio 3, mm. 1-4, 2 appearances; Inventio 4, mm. 1-6, 3 appearances), or with changing harmonic support (Inventio 1, mm. 1-2, 4 appearances; Inventio 7, mm. 1-2, 4 appearances). Keep in mind that this style of imitative opening is only one of two types of invention beginnings. The other type might be called the contrapuntal associate, where two equal voices begin simultaneously and there is no imitation, as illustrated in Inventio 5, 6, 9, 11, 12, 14, and 15.

As a model for the imitative opening, we will focus first on Inventio 1. Notice how the first two appearances of the motive begin on the same pitch-name (C), and imply the same harmonic accompaniment (tonic). The next two appearances, in m. 2, again both begin on the same pitch-name (G), and imply dominant harmony. Measure 3 continues the tonic-dominant progression in mm. 1-2 by resolving the harmony back to tonic. Notice further that while the motive in the upper voice at the beginning of m. 1 is imitated by the lower voice, the upper-voice countermotive in the last half of m. 1 is not imitated by the lower voice in m. 2. This is very important to realize. It would've been impossible for the lower voice to continue at the beginning of m. 2 with the countermotive from the end of m. 1 since that countermotive implies tonic harmony, and the beginning of m. 2 is already on dominant harmony. Notice finally that the lower-voice imitation at the end of m. 2 does not close with an ascending 5th skip (G-D), as did the motive at the head of m. 2. Instead, it closes with a 4th skip (G-C). The end of the motive is altered so that dominant harmony of m. 2 can resolve to tonic harmony in m. 3. Compare this exposition with that of Inventio 7.

A second type of imitative exposition is illustrated by Inventio 4. There, the imitation do not shift from tonic to dominant harmony. Rather, all appearances of the motive begin on the same pitch-name (D), and all imply tonic harmony. The motive itself (mm. 1-2) does, of course, imply a progression from tonic to dominant (and then resolves back to tonic in m. 3). Inventio 8 and 13 also illustrate this type of imitative opening.

Contrapuntal Associate
Inventio 5 illustrates well the contrapuntal associate. Both voices begin simultaneously, on tonic, complementing one another melodically and rhythmically, and lead eventually to a restatement of the voice pairing but with parts reversed, starting at m. 5, but this time on dominant harmony. Inventio 11 follows this plan as well, somewhat modified (NB mm. 3-4!). The dominant-harmony presentation begins at m. 7. See also Inventio 9 (dominant statement begins at m. 17) and 14 (dominant statement begins at m. 6. In sum, there are two basic types of invention openings, the imitative and the contrapuntal associate. The imitative type has two subtypes: tonic/dominant alternation and all tonic entries of the motive. In the type based on the contrapuntal associate, the voice pairing is presented first in tonic and then, possibly after a transition, in or on dominant.

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