On August 21, 1772 the Salzburg archbishop Colloredo appointed the 16-year-old Wolfgang Amadeus Mozart as concert master in his orchestra, at an annual salary of 150 gulden. During the following years, Mozart wrote the majority of his concertante works for violin and orchestra, beginning with the Violin Concerto in B flat, K.207 (1773) and the Concertone for two violins, oboe, cello and orchestra, K.190 (1774). These were followed in 1775 by another four violin concertos (in D, K.211; in G, K.216; in D, K.218; and in A, K.219); and a few years later, during the summer or early autumn of 1779, he wrote the final work, his Sinfonia Concertante for violin and viola, K.364.
The genre of the sinfonia concertante - which was usually written as a three-movement work, in which a number of soloists enter into a dialogue with the orchestra - was hugely popular for a short while. No less than 500 works in this genre have come down to us, of which the majority were written between 1770 and 1830. The generally light-hearted and amusing character of most of these works is most striking. Mozart probably first came into contact with the sinfonia concertante on his trip to Paris in 1777/1778: perhaps during the journey itself in Mannheim, where mostly concertantes with solo wind instruments were being written, and otherwise certainly in Paris, where Ignaz Pleyel - among others - was enjoying great success with his concertantes. If the Sinfonia Concertante K.297b for oboe, clarinet, horn, bassoon and orchestra is indeed by Mozart, then he must have written this work for his friends in Mannheim. However, the authenticity of this work is debatable. It has definitely been established that Mozart began work on a composition for violin, viola and orchestra upon his return to Salzburg, at a time when he was in fact losing interest in the violin. The piano was increasingly gaining ground as his favourite instrument. Was this Sinfonia Concertante perhaps a commission for a special occasion? This seems the obvious conclusion, as a fragment of 134 bars has also come down to us, from the first movement of another Sinfonia Concertante in A, for violin, viola, cello and orchestra.
Thus the Sinfonia Concertante in E flat is Mozart's only authentic contribution to this genre. And what a contribution it is! Alas, we remain largely in the dark with regard to the background of this masterpiece. Mozart does not mention it in his letters; there are no other documents referring to this work; and what remains of the manuscript is incomplete and also contains parts of various ‘previous versions' of the work.
Mozart's Sinfonia Concertante forms a lonely highlight in the genre. The work is of symphonic dimensions, yet is also a full-blooded double concerto. As in his violin concertos, here Mozart treats both solo strings like singers in a scene from an opera. The slow movement, especially, could easily be a duet from one of his operas.
Furthermore, the Sinfonia Concertante is the only concerto composed by Mozart for the viola, the instrument he himself loved to play. His vast understanding of the instrument is apparent from the key he chose: as the viola part is written in D, the instrumentalist needs to tune his instrument half a tone higher (scordatura), producing a more transparent sound, which mixes better with that of the violin. It also means that the violist is able to make use of more open strings, which almost automatically lifts the sound above that of the orchestra.
A remarkable feature is that Mozart regularly employs a serious tone in the work, which is contrary to the light-hearted character of the genre. Compared to the five violin concertos written four years previously, this work is far more mature. Then again, a lot had happened during those four years. Mozart's journey to Paris had ended in disappointment; furthermore, he had lost his mother in the French capital; then he had fallen head over heels for Aloysia Weber, who unfortunately did not reciprocate his feelings. On his way home, he wrote as follows to his father: "Ich habe ein gar zu empfindsames Herz" (= my heart is far too sensitive), a line which could have come straight from Goethe's book "Das Leiden des jungen Werthers". Although Mozart probably had not read this novel, written five years previously, it is tempting to recognize a similar melancholy and ‘Empfindsamkeit' in the slow movement of the Sinfonia Concertante. The soloists sing a duet against the background of an obscure-sounding orchestra (with divided violas). At times they comment on each others' words, at others they sing together in consonant intervals. During the third movement, all melancholy disappears as if by magic. In this work too, Mozart avoids the minor key. At a certain moment, when the music threatens to change to the key of C minor, he suddenly breaks off and shamelessly permits the viola to continue in the key of A flat. Instead of a cadenza, this movement ends with a passage in which each soloist shoots up, in turn, like a rocket to the highest register: an effect that Haydn was to imitate in his own Sinfonia Concertante dating from 1792.
The trunk which Mozart took with him on his journey to Mannheim and Paris probably also contained another work, which is closely related to the Sinfonia Concertante: the Concertone for two violins, oboe, cello and orchestra. In the development of the concertante forms, the concertone is ranked in between the concerto grosso and the sinfonia concertante. The genre was mainly intended as light entertainment, and the soloists are not expected to perform any virtuoso antics. In Austria and in the north of Italy, the concertone flourished for a short period, but apart from Mozart's compositions, few other concertones have come down to us. However, Leopold Mozart used the title ‘concertone' when referring to certain compositions by Mozart's colleague, Josef Myslivecek. It is interesting that the manuscript of the Concertone is part of a collection of three bundles of manuscripts which were compiled by Leopold Mozart, and came into the possession of the publisher August Cranz via Schubert's friend Leopold von Sonnleithner, among others. Apparently, Leopold Mozart compiled the three bundles according to genre. The first part contains the great Serenade K.185 with the corresponding March K.189. The third part contains nine symphonies, written between April 1773 and April 1774. In the second part we encounter three serenades (K. 203, K.204 and K.250), as well as the Concertone. Leopold Mozart probably considered the genre of the concertone to be an extension of the great serenades: after all, these also contain a number of movements with one or more instrumental soloists.
It is not inconceivable that Mozart performed the Concertone in Mannheim or Paris: after all, he had written this earlier in 1774, i.e. directly after his first violin concerto. However, as in the case of the Sinfonia Concertante, there are no known documents that can provide any further information in this respect.
The fact that Mozart wrote alternative movements for two concerts proves that his violin concertos were performed not only by himself, but also by others (for instance, by his Salzburg colleague, Antonio Brunetti). There is nothing to relate the Rondo in C, K.373 with one of Mozart's own violin concertos; therefore, it is more probable that Mozart intended the work to be an independent concert rondo. Brunetti played the composition on April 8, 1781 during an Academy in the residence of Prince Rudolph Joseph Colloredo, the father of the Salzburg archbishop who gave Mozart such a hard time.