Bach's concertos for violin are thought to have been written between 1710 and 1720, roughly at the same time as the "Brandenburg" Concertos. They were undoubtedly composed after Bach had studied Vivaldi's concertos, which became the talk of the musical world after the publication of his Op. 3 collection in 1711. In the D-minor Concerto for Two Violins, echoes of Vivaldi, and the outgoing Italian style generally, are heard in the brisk, aggressive character of the outer movements, and much of the solo writing.
The first movement begins as a muscular but dizzyingly intricate fugue, becoming simpler and more direct when the soloists enter with their own contrapuntal material and the orchestra labors to get an occasional word in edgewise. The third movement is, if anything, even more vigorous, with the soloists tumbling over each other in close counterpoint.
The justly famous middle movement is a world unto itself, with its own sense of time. The orchestra sets up a gentle rocking in the rhythm of the siciliana, over which the violins weave imitative lines in a constant chain of dissonance resolving into consonance, creating a sensual, and poignantly beautiful, ebb and flow of tension and ease.
-- Lawyer and lutenist Howard Posner has also annotated programs for the Los Angeles Baroque Orchestra, the Coleman Chamber Concerts, and the Salzburg Festival.