Although there is no standard form in Bach's Inventions, there are a few typical formal types, based
on the number of sections devoted to presenting the motive:
- two-part form with recall (quasi-recapitulation)
- two-part form without recall
- three-part, recapitulatory form
A codetta often concludes the piece.
We will call the sections devoted to the motive (where the motive reappears) presentations.
The presentations are generally linked together with modulatory sections, which we will call episodes.
The presentations vary and transform the motive. Episodes, which are melodically derived from
the motive, are modulatory; they lead from key to key and result in an overall tonal design.
Two-part form with recall: Inventio 5
Measure 1 presents the basic motive in the right hand; the left hand counterpoints
it (as a "contrapuntal associate"). Measure 2 re-presents the motive and the
piece then continues with new material leading to a left-hand, dominant-key
presentation of the motive and contrapuntal associate. The exposition ends
on the downbeat of m. 9, and a modulatory episode begins there and runs through
the downbeat of m. 12. The exposition together with the episode constitute
section 1. Section 2, a new presentation of the motive, begins in m. 12 and
runs through the downbeat of m. 20, where another modulatory episode begins,
and continues through the downbeat of m. 27. The recall starts in m. 27 (recalling
the opening of the piece) and leads to a short codetta (mm. 30-32).
- Section 1: mm. 1-12 (exposition, mm. 1-9; episode, mm. 9-12)
- Section 2: mm. 12-21 (presentation, mm. 12-20; episode, mm. 20-27
- Recall: mm. 27-32 (recall, mm. 27-30, codetta, mm. 30-32)
Two-part form without recall: Inventio 8
Measures 1-2 present the motive in the right hand, which is imitated canonically
in the left in mm. 2-3. The exposition ends on the downbeat of m. 4, and there begins
the post-expostion, modulatory episode, which ends on the downbeat of m. 12 (= section
1). A dominant-key presentation begins in m. 12 and continues up through the downbeat of
m. 19, where another modulatory episode begins. It lasts up through the downbeat of m.
26. The remainder is a codetta.
- Section 1: mm. 1-12 (exposition, mm. 1-4; episode, mm. 4-12)
- Section 2: mm. 12-26 (presentation, mm. 12-19; episode, mm. 19-26)
- Codetta: mm. 26-34
Three-part (recapitulatory) form: Inventio 3
The motive occupies mm. 1-2, and is imitated in mm. 3-4; the subsequent
measures, up through m. 12 (end of section 1), are its modulatory aftermath
(Fortspinnung, "spinning-out"). A dominant-key presentation begins
in m. 12, and initiates a modulation (to B minor). Measures 18ff establish
and reinforce the key. A B-minor presentation begins in m. 24, overlapping
with the close of the preceding presentation. This new (B-minor)
presentation and its modulatory Fortspinnung continues up through the downbeat
of m. 42, a half cadence in D major, the "home" key. The final section,
a recapitulation, begins in m. 42, and leads to an deceptive cadence in m.
54 (an aborted perfect authentic cadence). The remainder is a codetta.
- Section 1: mm. 1-12 (exposition, mm. 1-5; episode, mm. 5-12)
- Section 2: mm. 12-42 (presentations in A:, mm. 12ff, and b:, mm. 24ff, both modulatory)
- Section 3 (recap.): mm. 42-59 (mm. 42-54, ending with a deceptive cadence; codetta, mm. 54-59)
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