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-Schwedt Brandenburg-Schwedt Brandenburg-Schwedt was a secundogeniture of the Hohenzollern margraves of Brandenburg, established by Prince Philip William who took his residence at Schwedt Castle in 1689. By appanage, they administered the manors of Schwedt and Vierraden on the Oder river (Uckermark and Neumark) as well as Wildenbruch in Pomerania (present-day Swobnica, Poland). Though prosperous, the cadet branch never obtained Imperial immediacy. Because of a lack of money in the late days of the disastrous Thirty Years' War (1618–1648), the "Great Elector Frederick William of Brandenburg in about 1640 mortgaged the Schwedt region to the Baltic German noble Gustav Adolf von (Varrensback,