Not counting his early attempts to the genre, Mozart headed for the sonata form relatively later in his creative life. The sonatas, K.6 to K.9 published as "Sonatas for the harpsichord with an optional accompaniment of violin, by J.G. Wolfgang Mozart from Salzbourg aged seven" are followed in 1765 by six sonatas, again with optional violin or flute part: K.10 to K.15. Same year six new sonatas and a series of variations preceded what we know today as his "real" piano sonatas. There are 18 of them starting from K.279. It should be noted that each series of Sonatas are separated by a relatively long period of time. The first six Sonatas (K. 279 to K.284) are from 1774, the next six (K.309 to K.311) and the ones K. 330 to K.333 are composed three to four years later: between 1777 and 1778. From 1778 to 1784 Mozart did not compose any Sonata except the one in C minor K.457. During this lap of time he concentrates on other forms, specially piano concertos. Simultaneously, some of his most beautiful symphonies are from the same epoch: the "Haffner" and "Linz" as well as the magnificent "Symphonie concertante" for violin and viola, K.364. In 1782 he composes string quartets and make a tremendous success with the "Die Entführung aus dem Serail". The following year, the apex of his religious music: Great Mass in C minor, K. 427 is performed. The last series of piano sonatas: K.535, 545, 570 and 576 are composed after this period of intense creativity between 1788 and 1789. All sonatas by Mozart are in a three-movement form. The traditional formal structure of the classical sonata: a first movement with two contrasting themes followed by a slow movement and concluded with a Rondeau or similar fast and brilliant section is applied in almost all his piano sonatas. For three of his sonatas Mozart changes that formal scheme: the Sonata in E-flat major K.282 starts with an Adagio followed by two menuettos and a finale, Allegro; the sonata in D major K.284 starts with an initial Allegro but is followed by a mid-movement named "Rondeau en Polonaise" and the ending is one Andante followed by twelve variations. Finally the famous "Turkish March" sonata in A major K.331 starts with an "Andante grazioso" followed by six variations, the middle movement is a Menuetto and the finale is again a Rondeau: the famous "Alla turca" (Turkish March). Mozart was not an innovator in the genre of the piano sonata like Beethoven was. His sonatas do not encompass his entire career and are not among his most important works. Yet in each of his "series of sonatas" we met with a composer in another stage of his creative life, a composer who already created the most significant works on that particular stage. Series one: Sonatas from K.279 to K.284: The series of six sonatas K. 279 to K. 284 starts the entire series of 18 piano sonatas by Mozart.The first five are from 1774, Mozart resides then at Salzbourg and he is to take a trip to Munich, there he will compose the D major one K. 284 the only sonata of the series which is going to be published during the lifetime of the composer. Those sonatas somewhat well known by younger pianists are actually not "easy" pieces. A strong influence from Haydn's sonatas N. 21 to 26, published about the same time can be spotted. Specially a sharp resemblance between the sonata in F number 23 by Haydn and the K.280 sonata by Mozart can not be missed. Simultaneously the effect of Carl Philipp Emmanuel Bach is visible specially in the slow movements and the opening bars of fast movements, for instance the beginning of the sonata in G major K.283. A strong and unmistakable "style galant" shows a composer perfectly "in tune" with the "Salzbourg way of life" of the time. Sonata in C major K.279 The starting Allegro in 4/4 is one extremely brilliant movement, according to Alfred Einstein an improvisatory style is detected specially with the running lines of the right hand. The development starts unsuspectingly in the key of G minor and modulates with a great deal of expressiveness. The re-exposition is ornamented with many interesting variations in the thematic materials. The F major Andante is a gracious aria decorated in its middle section with elegant triplets. The 2/4 finale, Allegro, is again in the sonata form with two themes. The first of them with fast lines is less developed than the second with repeated notes which dominates the development and recapitulation sections. Sonata in F major K.280 The Assai allegro in 2/4 is based on two themes separated by a section in triplets which will also serve as the starting point of the development. The slow movement in F minor in 6/8 is the only slow movement in all 18 sonatas in a minor key. The movement is based on a theme in "sicilienne" form with an almost pathetic melancholy. Sonata in B-flat major K. 280 A rigorous sonata form in 2/4 which is slightly more extended than the previous sonatas. Both of its themes are very contrasted and the rhythmical variety within the movement is constant. The Andante amoroso in E-flat major, 3/8 exhibits a gracious and refined melody. The sonata ends with a Rondo, Allegro in 2 extremely elaborated around its joyful theme. This movement exhibits the mastery of the young composer. An added tension is built with the second section in G minor. Sonata in E-flat major K. 282 Unusual sonata which begins with an Adagio in 4 whose lyrical and melodic motives, sometimes tormented, shows the influence of Johann Christian Bach. In the middle part two menuettos bring a delightful grace and a mono-thematic Allegro in 2/4 concludes the piece. Sonata in G-major K. 283 Both themes of the starting Allegro in 3/4 have the gracious beauty of Johann Christian Bach. Mozart takes a step forward by beginning his development with a new motive. The C-major Andante is in three parts with in the middle a dark section in c-minor. The sonata ends with one exuberant finale as Presto in 3/8.