Although Bach dedicated these concertos to the Margrave of Brandenburg in 1721, they were not composed anew for him. The instrumentation for these works was much more suited to the orchestra that Bach was then working with, that of the court of Prince Leopold of Anhalt-Cothen. Bach's composition in the concerto form was influenced by the concertos of Vivaldi especially, but represent a stylistic advance in the genre.
Brandenburg Concerto No. 4 was perhaps the last of the six to be composed and more closely resembles a concerto grosso than a solo concerto. While the solo group of the violin and two recorders is often opposed as a unit to the larger ensemble. In the 1730s, Bach transformed this piece, substituting harpsichord for the solo violin and transposing it from G major to F major. The solo instruments in Brandenburg concerto No. 5 -- harpsichord, violin and flute -- operate more independently of the remainder of the ensemble; the second movement is scored for the solo instruments alone. The harpsichord gradually becomes the predominating solo instrument by the end of the first movement, effectively making this the first harpsichord concerto. The harpsichord is given a cadenza at the end of the first movement, unusual for both its length and the fact that it continues the musical narrative instead of interrupting it. For the orchestra, the normal second violin part is completely omitted.
The orchestra of Concerto No. 6 completely omits all violins. The solo group of two violas and cello are contrasted with instruments considered to be the core of a basso continuo complement: harpsichord, violone, and two violas da gamba. This standard Baroque instrumentation suggests that this concerto may have been the earliest to be composed.