The Sonata in C minor, BWV 1017, is the fourth of a set of six that Bach composed for violin and harpsichord in which he liberated the keyboard from the filler functions of continuo accompaniment, creating true partnership with the solo violin. The structure is that of the Italian sonata da chiesa, or church sonata – four movements, slow-fast-slow-fast. In the slow movements of this Sonata Bach gives the violin two of his great cantilenas, long lines spun out over broken chords in the right hand of the keyboard. The first is a Siciliano and one of Bach’s most famous melodies; the second a poised reflection in the relative major mode that serves as a prelude to the finale. The fast movements are basically abstract dances, in which the violin and keyboard swap material back and forth in buoyant counterpoint.