The two-part Inventions BWV 772 a 786 (originally named praeamblae) are short pieces written for harpsichord by Johann Sebastian Bach in Köthen between 1717 y 1723.

According to Bach:

Forthright instruction, wherewith lovers of the clavier, especially those desirous of learning, are shown in a clear way not only 1) to learn to play two voices clearly, but also after further progress 2) to deal correctly and well with three obbligato parts, moreover at the same time to obtain not only good ideas, but also to carry them out well, but most of all to achieve a cantabile style of playing, and thereby to acquire a strong foretaste of composition.

We will classify the inventions according to the structure and compositional techniques used:

Category	Description	Inventions
Single subject	Based on a single subject, the structure is similar to a fugue with presentations of the subject connected by episodes.	1, 3, 4, 7, 10, 13, 14, 15
Double subject	Based on two subjects. Episodes between subjects presentations modulate to several closely related keys in a fugue-like way.	5, 6, 9, 11, 12
Canonic	Make extensive use of the canon contrapuntal technique.	2, 8

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