Keyboard concertos by Johann Sebastian Bach left Weimar in 1717. Many of Bach's orchestral harpsichord concertos are adapted from a model with one or more violin solo parts. Several of these earlier models are extant. The oldest of these is Vivaldi's concerto for four violins, RV 580, published in 1711, model for Bach's concerto for four harpsichords, BWV 1065. Bach replaced the part of his fourth "Brandenburg Concerto", BWV 1049, composed in 1721 or earlier, by a harpsichord part when he reworked it to the harpsichord concerto BWV 1057. Bach's extant violin concertos BWV 1041–1043, two for a single violin soloist and one for two violin
Brandenburg Navy Brandenburg Navy had almost thirty active warships. These ships were used primarily to secure control over hostile trade routes and maritime trading, as blockades and to provide naval defence, and to also provide reinforcement on various military operations, which would frequently involve engagements with unfriendly warships. In 1682, Frederick William, the prince-elector of Brandenburg, who was intensely involved in the navy's affairs, secured the navy a base at Greetsiel, but they shifted to Emden a year later. Frederick William died in 1688, and his descendants took no interest in the Brandenburg Navy. Frederick III and his grandson Frederick the Great