Rarely can say with such precision when a piece was written: according to Mozart, he composed this violin sonata in G major on Saturday, April 7, 1781, between 11:00pm and midnight. Even for Mozart, writing a 25-minute sonata in a single hour was an incredible feat—and indeed, that first version was more of a sketch for the violinist, against which Mozart played by memory on the keyboard for a concert the following night. The version he finally wrote down in full gives no hint of a rush job, but it does have a concentrated flow and an inky, nocturnal spirit suggesting the setting of its composition. Mozart wrote the sonata in his last year working for the archbishop at the Salzburg court, and premiered it with Antonio Brunetti, the concertmaster of its orchestra.
The first movement begins with a dusky theme in rolled chords for the piano alone (indeed, Mozart considered the violin—not the piano—to be the accompanying instrument, even as his sonatas of the 1780s established greater equality between the two instruments). The violin joins in a repetition of the phase, and they go on their way, elaborating on the introspective melody. The second half of the movement is an Allegro, set mostly in G minor, and of a bolder character. The final movement is a theme and variations, once again relatively slow, but capped by a return of the opening and a livelier coda.