Bach's Concerto for Four Harpsichords and String Orchestra in A minor is an adaptation from around 1730-1733 of Vivaldi's B minor Concerto for Four Violins and String Orchestra in B minor, No. 10/3. Bach had gotten to know Vivaldi's Op. 3 while an organist at Weimar, where he transcribed ten of them for solo harpsichord and six of them for organ. This later adaptation is far more ambitious. In it, Bach has both tightened and expanded Vivaldi's counterpoint, enriched his harmonies with lusher harmonies, and expanded the solo parts with greater complexity and greater clarity. The result is a work that not only avoids the criticism of being too thickly textured, but actually improves on the original work. Written in the standard three-movement concerto form of the Baroque period, Bach's Concerto for Four Harpsichords is a brilliant virtuoso piece for the soloists.
