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
Brandenburg end, and from 1323 up until 1415 Brandenburg was under the control of the Wittelsbachs of Bavaria, followed by the Luxembourg Dynasties. Under the Luxembourgs, the Margrave of Brandenburg gained the status of a prince-elector of the Holy Roman Empire. In the period 1373-1415, Brandenburg was a part of the Lands of the Bohemian Crown. In 1415, the Electorate of Brandenburg was granted by Emperor Sigismund to the House of Hohenzollern, which would rule until the end of World War I. The Hohenzollerns established their capital in Berlin, by then the economic center of Brandenburg. Brandenburg converted to Protestantism in