The last movement opens with an orchestrated version of Bach's setting of "Dir, dir, Jehovah, will ich singen," with each half of the chorale repeated. Thereafter, soloist and orchestra alternate and share equally as they present varied iterations of this borrowed material. The first variation (mm. 19–52) introduces new embellishments and livelier rhythms, concluding with a triplet melody in the first violins. The second variation (mm. 52–83) is livelier still, with sixteenth-note figuration in the solo part over delicate pizzicato accompaniment, alternating with equally ebullient statements of each half of the chorale tune in the first violins. A dramatic E-minor fugato whose subject is based on the first four measures of the chorale melody ensues in the strings (mm. 83–100), building up to a startling reentry of the harpsichord in its highest register as it repeats the first half of the chorale tune in A minor over crystalline scalar figuration. This variation is greatly extended and fantastically elaborated into a quasi-development section (mm. 107–36) which motivically recalls the chorale tune while at the same time discovering new material and presenting the harpsichordist with an opportunity for virtuosic flights of fancy. After a short fully notated cadenza, the meter shifts from 3/4 to a sprightly alla breve and the fugato texture resumes as the second violin, viola, and first violin present the four-measure subject in an entirely new guise (with reinforcement from cello and harpsichord). The soloist enters with yet another novel variation of the first half of the chorale tune, emphasizing this time not its melodic contour but its underlying harmonic structure (mm. 152–60). The movement concludes with a brightly animated tutti version of the second half of the chorale melody, topped off with an arpeggiated flourish deftly delivered by the soloist.