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 Brandenburg Brandenburg (; , Lower Sorbian: "Bramborska", ) is a state of Germany. Brandenburg is located in the northeast of Germany covering an area of and has a population of 2.5 million residents, the fifth-largest German state by area and tenth-most populous. Potsdam is the state capital and largest city, while other major cities include Brandenburg an der Havel, Cottbus, and Frankfurt (Oder). Brandenburg surrounds the national capital and city-state of Berlin, which together form the Berlin/Brandenburg Metropolitan Region, the third-largest metropolitan area in Germany. Brandenburg borders the states of Mecklenburg-Vorpommern, Lower Saxony, Saxony-Anhalt, and Saxony, and an international border