Sinfonia Concertante in E flat major for violin and viola, K.364

There is only one concerto for violin and viola. It is true that Mozart called it a Sinfonia Concertante and that there are many similar works scored for the same two instruments. There might even have been a model - some now forgotten Symphonie Concertante heard on the composer’s recent visit to Paris perhaps - that Mozart had in mind as he worked on the piece in Salzburg in the summer of 1779. But no concerto or concerto-like work for violin and viola written before or even after Mozart’s Sinfonia Concertante has survived into the present-day repertoire.

Mozart at the time was uniquely well equipped to create the definitive example of the genre. He was an accomplished performer on both instruments, with a particular affection for the viola, and he was writing at a time before the violin had assumed the heroic character that made it a natural partner for the cello rather than the viola. He also had the imagination to enrich the darker colours of the orchestra by dividing the violas into two parts and at the same time to brighten the sound of the solo viola by having it tuned a semitone higher than usual. So for once violin and viola can converse on equal terms. In the outer movements Mozart is scrupulously fair in sharing the thematic and bravura interest between them, not least in the fully written out cadenzas. In the central Andante he discreetly allows the viola to express itself just a little more elaborately than the violin - which is one source of the peculiarly rueful beauty of this movement.