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
Horn Concertos (Mozart) Horn Concertos (Mozart) The Horn Concertos by Wolfgang Amadeus Mozart were written for his friend Joseph Leutgeb whom he had known since childhood. Leutgeb was a skilled player, as the works are very difficult to perform on the natural horn of the period, requiring lip trills, much hand-stopping, and rapid tonguing. In addition to the four works listed above, there are two incomplete concerto movements, K. 370b and the Concert Rondo, K. 371, both from 1781 and both in E-flat major, and a 91-bar fragment of the first movement for a concerto in E major (K. 494a), written in 1785