A string quintet ensemble is usually made up of a string quartet; two violins, viola and cello, with the addition of another cello or viola. On occasion a double bass may be one of the extra instruments. The two string quintets Mozart wrote in 1787 have an additional viola added, because reportedly Mozart's favorite stringed instrument to play was the viola.
The pair of quintets are a study in contrast, as the one in C major is of a decidedly more sunny disposition than the one on G minor, a key that seems to be Mozart's key of passion and deep feeling. He wrote the pair of quintets around the time of the composition of his opera Don Giovanni, as well as the final illness of his father.
I. Allegro - The movement begins straight away with a hushed, agitated theme played in the first violin to an accompaniment from the second violin and first viola:
II. Menuetto: Allegretto - The second movement minuet is far removed from the original courtly dance. It is in G minor, and is punctuated by two loud chords heard on the 3rd beat of the 4th and 6th bar:
III. Adagio ma non troppo - Played with mutes on all five instruments throughout its length, the third movement is in E-flat major. Mozart's chromatic transition to the second theme in B-flat minor is taken up again as this minor key theme transforms into B-flat major and is repeated. The music delves back into despair once more before the sweetness of E-flat major brings the movement to a close.
IV. Adagio - Allegro - Mozart begins the final movement in the darkness of G minor once again. But after the music shifts tempo, key to G major in 6/8 time, The preceding dark movements are balanced out by this rondo, as is in full keeping with the music aesthetic of the Classical era.