Sonata in B minor BWV1030 (c.1735)

Bach was not the first to write sonatas for a wind or string soloist with an “obbligato” accompaniment: that is to say with a keyboard part which not only supplies the harmonies – its humble function in most sonatas of the day – but also joins in a genuine dialogue on equal terms with the solo instrument. He was, however, the greatest composer among his contemporaries to do such a thing and the most effective in establishing the duo sonata as a true chamber-music medium.

Though outstanding among the four works of this kind for flute and harpsichord, the Sonata in B minor was probably not written in that form in the first place. It is believed to have originated in a trio sonata for two flutes and continuo or a concerto for flute and strings. The resourcefully extended construction of the first movement, which alternates “tutti” sections devoted to the main theme with brilliantly inventive solo episodes, seems to support the concerto theory. The expressive Largo e dolce would not be out of place in a concerto either. On the other hand, the last movement, where a three-part Presto fugue in common time is followed by a virtuoso gigue in 12/16, could well have derived from a trio sonata.