Piano concertos by Wolfgang Amadeus Mozart it was probably J.C. Bach, whom Mozart admired, who introduced the structural innovation of allowing the keyboard to introduce new thematic material in its first entry. Concertos Nos 1–4 (K. 37, 39, 40 and 41) are orchestral and keyboard arrangements of sonata movements by other composers. The next three concertos (K. 107/1, 2 and 3), which are not numbered, are arrangements of piano sonatas by J.C. Bach (Op 5. Nos. 2, 3, and 4, all composed by 1766). Based on handwriting analysis of the autographs they are believed to date from 1771–72. Concerto No. 5, K. 175 from 1773 was
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