There were precedents for Wolfgang Amadeus Mozart’s string quintets, especially in the works of Luigi Boccherini, who wrote hundreds of quintets for two violins, viola, and two cellos. Furthermore, writing string quintets was not such a far cry from writing string quartets, whose huge possibilities had begun to come clear in the great works of Joseph Haydn. But there was something about the quintet with two violas that brought out the best in Mozart. It is as though the form of the string quartet presented itself with just enough lyric anarchy added (in viola form) to allow operatic activity to break loose: plots, schemes, subplots, finales, arias, and so on. Mozart’s string quintets are extraordinary feats of musical invention.
Very broadly speaking, the D Major quintet seems to create a sort of narrative sequence over its movements. Two beautiful slow sections (almost) frame the first movement, and the main body of the movement has a fairly straightforward, expository feel. The second movement, in the manner of an aria, takes elements from the first movement (using a melody shape from the Larghetto and a falling line from the Allegro of the previous movement) and explores their emotional conditions (very, very beautifully). The third movement is a minuet full of tricks, machinations, and rhythmic displacements; its trio expands slyly on the arpeggio figure (from the cello) that opens the first movement. In the last movement everything comes together — or blows apart — or both — around a strange chromatic figure in the main theme. (Mozart actually rewrote this figure in a more tonal way, but the odd original remains standard.) The mood of the last movement is complex: rhythmically quite bright, but tonally unsettled. So what seems like it ought to be a fairly usual concluding rondo turns into a large and argumentative situation — it has the feeling of an operatic finale, of problems arising from nowhere, complications falling from the sky, and solutions coming by chance.