I would like to open this essay by quoting from Charles Rosin’s book, “The Classical Style.”  On page 281 he says, “No other composer of the eighteenth and nineteenth centuries ever understood the demands of  writing for three voices as Mozart did, except for Bach in his trio-sonatas for double manual and pedal keyboard. As a string trio, this one of Mozart’s stands alone, far above all other works in that form.”

The string trio K 563 of Mozart sets itself up as being different from the usual chamber music for strings, not only by the fact that it uses only three stringed instruments, but by the fact that it contains more than the usual four movements of the traditional form, thus it is called a divertimento, i.e. a piece in several movements for an ensemble, alternating dance movements with movements in sonata and rondo form.

Mozart could create more excitement and interest with three voices than most composers could with six. Listening to this work, if you did not already know that it is a trio, you might swear it is a string quartet. Another aspect of this work is that Mozart gives all three instruments equal treatment, making it truly democratic. At times it is richly polyphonic.

The opening sonata-form Allegro is playful and happy, but takes on a more serious demeanor in its development section. With its sophisticated modulations and rich counterpoint, this is one of Mozart’s most intense development sections.

The Adagio which follows is one of Mozart’s most emotionally intense slow movements. It is broadly conceived and has great melodic beauty. This is followed by a minuet, which, though not as artful as the first two movements, is quite charming.

The fourth movement is a theme and variations movement which uses a catchy tune for its theme. Mozart treats variation form in the traditional manner in this movement, but of course, being by Mozart, it is full of inventiveness and beauty.

The fifth movement is another minuet, a bit more courtly than the first one, but not without certain rustic charms.

For the finale Mozart uses, as he usually did for finales, rondo form. Actually, it is sort of hybrid of sonata form and rondo form, with a central development section. It is a cheerful rondo with an infectious melody as its main theme. This movement has direct melodic appeal, but if you listen closely, it has so much more than mere melodic beauty. Its rich harmonic contrasts and its episodes of a more polyphonic character, are finely crafted. This finale cannot fail to please.