Sonata, K. 303 by Wolfgang Amadeus Mozart
for violin and piano

In Mozart's youth, the most popular of all chamber music forms was the "unaccompanied sonata", the sonata for piano with accompaniment for violin. The implicit understanding at that time was for the keyboard part to be played by a lady and a gentleman to "accompany" her on the violin. The form represented an apt musical analogy to the social custom of the day.

The first movement of the Sonata in C Major, K. 303, composed in 1778, follows a unique formal model which begins with slow music (a short Adagio), then changing keys into the dominant, G major, breaks into a lively Allegro. The Adagio returns in an elaborated form and with a twist stays in the home key of C major. When the point is reached where the Allegro restarts, it is now in the home key of C major and serves as an orthodox recapitulation. So in a single movement there exists normal sonata form but also incorporates slow music within the integrated whole.