earliest works are those found in Nannerl's Music Book. Between 1782 and 1786, Mozart wrote 20 works for piano solo (including sonatas, variations, fantasias, suites, fugues, rondo) and works for piano four hands and two pianos. Solo piano works Dual piano/performer works Piano four-hands Sonata in C major for keyboard four-hands, K. 19d (doubtful) (London, May 1765) Sonata for Keyboard Four-hands in D major, K. 381/123a (1772) Sonata for Keyboard Four-hands in B major, K. 358/186c (1774) Sonata for Keyboard Four-hands in F major, K. 497 (1786) Sonata in C major for piano four-hands, K. 521 (1787) Sonata for Keyboard Four-hands in G major, K. 357 (incomplete) (1786) Fugue in G minor, K. 401 (incomplete) (1782) Andante and Variations in G major, K. 501 (1786) Adagio and Allegro in F minor for a mechanical organ, K. 594 (1790) (organ, composer's transcription) Fantasia in F minor, K. 608 (1791) (organ, composer's transcription) Others Allegro in G major, K. 357/497a (1786-87; fragment) Two pianos Sonata for Two Pianos in D major, K. 448/375a (1781) Fugue in C minor for Two Keyboards, K. 426 (1783) (transcribed in 1788 for string quartet as K. 546) Larghetto and Allegretto for Two Pianos in E major, K. deest (completed by Maximilian Stadler) Others Allegro in C minor for Two Pianos, K.Anh. 44/426a (1783-86; fragment) Chamber music Chamber music with piano Violin music Mozart also wrote sonatas for keyboard and violin. For the most part, these are keyboard-centric sonatas where the violin plays a more accompanying role. In later years, the role of the violin grew to not just a support to the other solo instrument, but to build a dialogue with it. The 'Violin Sonatas', KV 10–15, are unique in that they include an ad lib. cello part along with the score for violin and keyboard. The Neue Mozart-Ausgabe (1966) therefore includes them along with the other keyboard trios, although the Köchel catalogue (K6, 1964) lists them as normal violin sonatas. Violin sonatas Childhood violin sonatas (1762–66) Violin Sonatas, KV 6–9 (1762-64) Sonata No. 1 in C for Keyboard and Violin, K. 6 (1762-1764) Sonata No. 2 in D for Keyboard and Violin, K. 7 (1763-1764) Sonata No. 3 in B for Keyboard and Violin, K. 8 (1763-1764) Sonata No. 4 in G for Keyboard and Violin, K. 9 (1764) Violin Sonatas, KV 10–15 (1764) Sonata No. 5 in B for Keyboard with Violin (or Flute)