the history of the sixth sonata bwv 1019 is distinct from that of the five others. the three different versions of the sonata and its successive comprehensive modifications in leipzig indicate that its role in the collection evolved only gradually. the two first movements, a large scale concerto allegro and a short largo, remained largely unaltered throughout these revisions and were copied by bach's nephew johann heinrich into the earliest surviving manuscript from 1725. the originals, assumed to date from cöthen, are lost; but it is probable that these were the first two movements of a three-movement "sonate auf concertenart." in the 1725 manuscript the remaining movements were entered by bach himself. the sonata took the following form: