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 and the lands of the Hevelli from their last Wendish ruler, Pribislav, in 1150. After crushing a force of Sprevane who occupied the town of Brandenburg in the 1150s, Albert proclaimed himself ruler of the new Margraviate of Brandenburg. Albert, and his descendants the Ascanians, then made considerable progress in conquering, colonizing, Christianizing, and cultivating lands as far east as the Oder. Within this region, Slavic and German residents intermarried. During the 13th century, the Ascanians began acquiring territory east of the Oder, later known as the Neumark (see also Altmark). In 1320, the Brandenburg Ascanian line came to an