Piano Concertos K. 107 (Mozart)
The Piano Concertos, K. 107 are three keyboard concertos by Wolfgang Amadeus Mozart, based on sonatas by Johann Christian Bach. These sonatas are from J.C. Bach's Op. 5; Mozart turned Sonata No. 2 in D, Sonata No. 3 in G, and Sonata No. 4 in E♭ from this set into the three concertos of K. 107.
These concertos remained unpublished in the Alte Mozart-Ausgabe, the first complete edition of Mozart's works, so they were not given a number by the publishers of that edition, Breitkopf & Härtel (as the other 27 concerti were given in that publication). Therefore, when these works are enumerated with the rest, it can be seen that Mozart composed 30 keyboard concerti. These three works, however, and the concerti numbered as Piano Concertos 1 through 4 are actually not original compositions, but arrangements of works by other composers.