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Form & Structure

Invention

Definition

An invention is a short keyboard piece in two-part counterpoint, built from one musical idea that the hands imitate and develop. The name comes from J. S. Bach's fifteen Two-Part Inventions.

An invention is a short contrapuntal piece for keyboard in which a single musical idea, the motif or subject, is passed between the voices and developed. The word is used mainly for J. S. Bach's fifteen Two-Part Inventions (BWV 772–786) and their companions, the fifteen Three-Part Sinfonias (BWV 787–801), sometimes called three-part inventions.

Why Bach wrote them

Bach wrote the Inventions and Sinfonias as teaching pieces. The preface to his 1723 fair copy explains their purpose: to teach keyboard players to play cleanly in two and then three parts, to develop a singing (cantabile) style, and to give them a taste of how to compose with good ideas. They are still core repertoire for intermediate pianists, as a step toward the larger preludes and fugues.

How an invention works

There is no fixed plan, but most two-part inventions follow a similar process:

  1. Statement: one hand plays the short motif, often in the home key.
  2. Imitation: the other hand repeats it, frequently an octave lower, while the first hand continues with a contrasting line.
  3. Development: the motif is moved through related keys using sequences, turned upside down (inversion), shortened, or combined with itself.
  4. Return: the motif comes back in the home key, and a firm cadence closes the piece.
A three-bar grand staff in 4/4. In bar 1 the right hand plays eighth notes E, C, D, E and quarters F, D, while the left hand rests. In bar 2 the left hand plays the same notes two octaves lower while the right hand plays quarter notes C, B, A, B. In bar 3 both hands hold a whole note C.
An original invention-style opening in C major. Bar 1: the right hand states a motif (four eighth notes and two quarter notes). Bar 2: the left hand imitates it exactly, two octaves lower, while the right hand adds a counter-line. Bar 3 closes on C.

The fifteen inventions are arranged by key, rising from C major: C major, C minor, D major, D minor, E-flat major, E major, E minor, F major, F minor, G major, G minor, A major, A minor, B-flat major and B minor.

Invention or fugue?

Both are contrapuntal and built from imitation. A fugue is usually larger and stricter: the subject enters in every voice at the start in a regular pattern, with an answer in the dominant. An invention is freer and shorter, more like a study in imitation.

Practicing an invention

  • Hands separately first, until each line sounds like a complete melody with its own shape.
  • Mark every appearance of the motif in both hands, including inversions.
  • Match articulation in both hands: if the motif is played detached in the right hand, play it the same way when the left hand imitates it.
  • Choose a calm tempo. Clarity matters more than speed.

The Two Lines, One Note at a Time and One Melody, Two Entrances worksheets practice the two-voice thinking an invention needs.

Common questions

What is the difference between an invention and a fugue?

Both use imitation, but a fugue follows stricter conventions: every voice enters with the subject in turn at the start, with an answer in the dominant. An invention is shorter and freer, built from a motif passed between two (or three) voices.

How many inventions did Bach write?

Fifteen Two-Part Inventions (BWV 772–786) and fifteen Three-Part Sinfonias (BWV 787–801), which are sometimes called three-part inventions.

Practice it: free worksheets