The Sinfonias, despite what the term suggests, are a set of three-part inventions for keyboard by J.S. Bach. They were originally written as musical exercises for his students toghether with the more technically accesible two-part inventions. The two groups of pieces are both arranged in order of ascending key, each group covering eight major and seven minor keys. The inventions were composed in Köthen; the sinfonias, on the other hand, were probably not finished until the beginning of the Leipzig period.