Form and Analysis

Invention

• Basic Features
  1. An invention is a musical composition based on a theme, or motive, that undergoes a series of transformations (thematic, tonal, and textural). It embodies the notion that a maximum amount of music is created from a minimum amount of material through the application of various developmental and contrapuntal techniques.
  2. An invention is sectional with regard to tonal scheme--that is, different sections exist, each having a different tonic than the preceding section. The composition is sectionalized by the presence of interior cadences. These cadences are, however, often weakened by the continuation of rhythmic drive or motion. In tonal writing, the keys are all closely-related.
  3. The basic motive is often called the theme, or subject.
     • The theme defines the key and rhythmic character of the composition. If the key is not clearly implied by the theme, a second voice is usually added for clarification.
     • The subject always has certain distinguishing characteristics.
     • The subject is usually either stepwise, in the mode of the composition, or outlines the tonic triad.
  4. A countertheme, or countersubject, may exist (material that consistently accompanies the subject).

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• Structural Aspects
  1. Initial statements: This is usually called the exposition. These statements alternate voices and are usually imitative at either the fifth or the octave. This section usually ends with a cadence in tonic or a closely-related key (the dominant or the relative major). The sequential, or developmental material that follows these statements is called an episode.
  2. Middle entries: These are complete statement of the subject usually in a key other than the original. There are typically two or three of these middle entries separated by episodes (almost always developmental in some way, usually sequential).
     • Episodes are passages based on a portion of the theme or countertheme, or, less often, on free material not related to either.
     • In an episode, the subject usually does not appear in complete form, unless its quite brief to begin with.
     • Typically, an episode serves to modulate from one key to another, and to provide a some contrast to the complete statements of the theme.
  3. Often times, the high point in the composition is reached approximately 2/3 to 3/4 of the way through.
  4. Final statements: The subject usually appears at the end of the composition in the original tonic, frequently in imitation. Sometimes, the final statements will be preceded by a dominant prolongation, heightening the effect of returning to the original tonic. Stretto may also appear in this final section. The composition ends with a strong final cadence.

   

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