Brandenburg Concerto No. 5 "Brandenburg Concertos" takes a central place. Nonetheless around half a dozen of Bach's extant concertos, including some of the "Brandenburg Concertos" and lost models of his later harpsichord concertos, seem to have had their roots in his Weimar period. Most of what Bach may have left with his employer in Weimar perished in a fire destroying Schloss Weimar in the 1770s. In 1719 a new large two-manual harpsichord arrived in the residence of Bach's then-time employer at Köthen. BWV 1050a, an extant early version of the fifth "Brandenburg Concerto", may have been conceived for this instrument, but that seems unlikely
Organ concertos, Op. 4 (Handel) however, has favoured the original intimate scoring for chamber organ and small baroque orchestra. In the 1940s the blind organist Helmut Walcha prepared a version for organ and second keyboard giving one possible ornamentation and extemporisitation of the organ part in the slow movements. Modern performing editions of Walsh's 1738 solo keyboard version and the original scoring for organ and orchestra have been prepared by the musicologists William Gudger and Terence Best. Organ concertos, Op. 4 (Handel) The Handel organ concertos Op 4, HWV 289–294, are six organ concertos for chamber organ and orchestra composed by George Frideric Handel in