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
Oberliga Berlin-Brandenburg each who would determine their champions in a home-and-away format. The two divisional champions would then play for the Brandenburg championship in a two-game series. Should each team win one game, a third game was held as a decider. The Brandenburg champion would then continue on to play in the German football championship. From 1925 onwards, the runners-up of Brandenburg was also qualified for an enlarged national championship. Below the league, as the second division in Brandenburg, four "Kreisligas" were set, those being: From 1925 onwards, until 1931, the league was dominated by Hertha BSC Berlin, who won it every