The Köchel Mozart catalogue entries K136 to 138 group three works identical in construction and written at the same time. These concise, self-confident, three movement works are more soloistic in character than designed for orchestral playing. Based on their “orchestration” they are string quartets. It is misleading to called them “symphonies”, as sometimes happens, because in the sense we understand the term today, they are not. Mozart did not employ the term Divertimento either, although it is more accurate, since in his day, the term signified “a small group of players”, which generally speaking meant one musician for each part. These works could be performed as string quartets, but performances with several instruments to each part can also be considered authentic.
Mozart composed his small series in early 1772, and if we regard them as string quartets, they are among his earliest. In some senses, they adhere to Italian models. Mozart and his father set off for Italy for the first time on December 13th 1769 and they stayed there for 15 months. Naturally, the journey made a decisive impact on the impressionable young Mozart. It was a kind of unorthodox “conservatoire” for him. He was able to appropriate the Italian musical styles and composition techniques which were indispensible in that era. In March 1770, he met Sammartini in Milan, who was the president of the local composers' circle, and his works privided Mozart with his string quartet models. The melodic world contained within each of these three Divertimenti's slow movements is profoundly Italianate.
Other influences can also be detected in these 1772 compositions: clearly Mozart knew the string quartets of Michael and Joseph Haydn. The leading role of the first violin, the prominence given to the central section of the movement and the development, as well as the richness of modulations, are all attested phenomena of the Haydn brothers. Mozart's natural instinct was to assimilate and integrate every influence into his own style, and he clearly could not resist such a “contemporary” solution either. The closing movement of the D major Divertimento also follows in Michael Haydn's footsteps. The development section in this movement takes on greater importance, and Mozart introduces a brief contrapuntal section, which was later to become almost a cliché in later Viennese classical style.
The similarities between the opening and closing movements is striking, and the question is undecided just how much this was a conscious compositional intention by Mozart. Otherwise, similar internal relationships can be found between movements throughout Mozart's mature oeuvre.