Violin Sonata in B flat major, K.378 (1779)

The classical violin-and-piano sonata began in Mannhiem in 1778 when Mozart wrote the first of the six Sonatas K301-306 that were published in Paris as “Opus 1” later in the same year. They were inspired by a set of six pieces by Joseph Schuster which had impressed him by being scored “à deux,” as he described it, rather than in the conventional manner of the sonatas of the day for harpsichord or piano “with violin accompaniment.” Certainly, the shared responsibility of violin and piano is one of the key features of the “Opus 1” Violin Sonatas and one that he was to develop in the next set, which would be published in Vienna in 1781 as “Opus 2.”

Although the Sonata in B flat major K.378 is one of the earlier works in the 1781 set - it was written shortly after the composer’s return to Salzburg from Paris in 1779, perhaps for his father and sister to play “à deux” - it is one of the most brilliant of all Mozart’s Violin Sonatas. It begins modestly enough with the violin providing a simple harmonic accompaniment to the delightful first subject on piano. But before the extensive exposition is complete, with second and third themes allotted to violin and piano respectively, there is a variety of spirited exchanges of bravura figuration between the two instruments. The development section which is based on yet another new idea, this one disturbingly introduced in F minor, is even more dramatically scored.

The Andante cantabile e sostenuto is surely the most developed slow movement written for violin and piano up to that time. An aria in E flat major, it includes a middle section beginning in the same key but presenting a new melody on the violin which accompanies its own song with some simple but attractively sonorous double-stopped harmonies. The same violin chords are enough in themselves to effect a token recall of the middle section before the end of the movement.

In the virtuoso spirit of the first movement, the triple-time Rondeau mischievously slips in an episode in common time in rapid triplet figuration before returning, with some ceremony, to the main theme and a coda enterprisingly coloured by multi-stopped pizzicato violin chords.