Keyboard concertos by Johann Sebastian Bach soloists, were all adapted into harpsichord concertos by the composer, BWV 1058, 1054 and 1062 respectively. It is often assumed that Bach's extant violin concertos were written in his Köthen period (1717–1723): it can however not be proven from documentary evidence that any of them existed prior to around 1730. In September 1725 Bach performed organ music, accompanied by other instruments, in Dresden. The works he performed there have not been identified. More than a year later he composed several cantatas with an organ obligato part. Several movements of such cantatas were derived from earlier lost concertos, and resurfaced in
Province of Brandenburg the Bear, another Saxon count from the noble House of Ascania, who established the Margraviate of Brandenburg in 1157. His son Margrave Otto I already achieved the dignity of an Arch-Chamberlain of the Holy Roman Empire in 1177. Emperor Charles IV by the Golden Bull of 1356 confirmed the electoral dignity of the Brandenburg margraves and in 1373 assigned the electorate to his son Wenceslaus in 1373. The Elector of Brandenburg held the seventh rank among the electors of the Empire and had five votes in the Council of Princes. In 1415 Brandenburg was acquired by Burgrave Frederick of Nuremberg,