The love and understanding between the genius and his sister (called affectionately Nanerl), the joy of their joint concerts are the impetus for the creation of several piano duets. Among them is the magnificent Concerto for two pianos and orchestra in E flat major KV 365. It was written in 1779, shortly after his return to Salzburg after a two-year European tour. The grown-up Amadeus visited Mannheim, Paris and Munich in order to find a more attractive job. He could not and he resigned (but not for long!) to the position of church organist under the Archbishop of Salzburg. In the series of new works he composed he infused the impulses from his fresh musical impressions of the French and Italian style. He focused on the Symphony-Concertante format, which marks Mozart’s masterful genres diffusion and created two exceptional examples in the same key – the Double Piano Concerto and the Concerto for Violin, Viola and Orchestra (KV 364). At that time, works for two solo pianos were a novelty, not many concert halls and homes had more than one piano. It is not historically clear when the KV 365 concerto premiered; most likely it was performed for the first time by Wolfgang and Nanerl. The concerto is scored in the traditional three movements, contrasting fast – slow – fast part. All the while, the composer enjoys the brilliant interaction between the two solo instruments, and the orchestra majestically intervenes in their fiery dialogue. The work is not just an attraction of virtuoso stunts; it bears a deep personal flavor – sharing music between two people with two pianos. At times the listener cannot distinguish between the parts of the soloists – one picks up a motif, phrase, passage, the other imperceptibly completes them. They playfully exchange remarks, jokes. They play together as one instrument, they compete.

The concerto is meant for Nanerl’s great piano abilities and, of course, for the composer himself – for four perfectly coordinated hands. Mozart praised his sister’s abilities and wrote in a letter to her: “Believe me, you can make big money in Vienna, for example, give private concerts and piano lessons. You will be in high demand – and well paid! ”. In his first years as a freelance artist in the capital of the Austro-Hungarian Empire, Amadeus performed this concert with Miss Josefine Auernhammer several times, until he grew tired of her obsessive love. To give more brilliance to the orchestral parts in the extremely fast parts, he added 2 more clarinets, 2 trumpets and timpani to the Viennese version. Unfortunately, the score of this second orchestral edition has not been found to this day.