Inventions are similar in style to a
fugue, though they are much simpler. They consist of a short
exposition, a longer
development, and, sometimes, a short
recapitulation. The key difference is that, unlike fugues, inventions generally do not contain an answer to the subject. Two-part and three-part inventions are in contrapuntal style.
Exposition In the exposition, a short
motif is introduced by one voice in the
tonic key. This is also known as the theme. The subject is then repeated in the second voice in the
dominant key while the initial voice either plays a
countersubject or plays in
free counterpoint.
Development The development comprises the bulk of the piece. Here the composer develops the subject by writing
variations either
melodically or
harmonically. This usually involves the alternation of episodes with statements of the theme, similar to the development of a
fugue. In minor- and major-mode inventions, the theme is typically restated in the
relative major and the
dominant, respectively. New key areas are reached through episodes, which usually move sequentially through the
circle of fifths. The final episode ends on a
half cadence in the original key, and is often exaggerated to make the subject sound extra special when it returns. Many of Bach‘s Inventions follow this plan, including
BWV 775 and
BWV 782.
Recapitulation If an invention does have any recapitulation at all, it tends to be extremely short—sometimes only two or four measures. The composer repeats the theme in the upper voice and the piece ends. The repetition of the theme contains very little variation (or no variation at all) on the original theme. The lower line usually plays the countersubject, and if there is no countersubject, plays in free counterpoint. ==History==