IF THERE IS ANYTHING THAT IS BETTER than a string quartet, it’s a string quintet. It seems incredible that one extra instrument (usually a viola, sometimes a cello) can add so much richness to the sound and so much variety to the contrapuntal and instrumental combinations.

Mozart, one of the greatest piano virtuosos of his time, was also an accomplished violinist (he called himself the best in the world!), but his favorite stringed instrument was the viola. When in informal quartet sessions with partners like Haydn and Dittersdorf and all three claimed the viola part, it was Mozart who won. His Sinfonia concertante, K. 364, for violin and viola was ground-breaking for the viola as a solo instrument, but it is in his six string quintets that he really declared his love with some of the warmest, most luxurious viola parts ever written before or since. The quintets are among the greatest works in the chamber music literature, a joy for the listener, pure bliss for the players.

The first quintet, in B-flat major, K. 174, was written in Salzburg in 1773 (a few months before Mozart’s 18th birthday), long before the others. Its many unisons, generally subordinate cello part, and brilliant scale passages hark back to the serenade, but it presages Mozart’s mature chamber music in its melodic inventiveness and skillful, many-faceted imitative counterpoint. However, it is rarely performed, having always been overshadowed by the later quintets.

Not until his last years in Vienna did Mozart return to the genre with two pairs of quintets, one written in 1787, the other between 1790 and 1791. It is thought that the first pair was intended as part of the customary set of six to be dedicated to the cello-playing King of Prussia for whom Mozart wrote his last three quartets; however, financial need forced him to sell them on subscription, along with an arrangement of his C minor Wind Serenade, K. 388.

The quintets represent Mozart at the height of his compositional and emotional power. Their command of structure, their daring modulations and contrapuntal complexity are awe-inspiring; their mercurial mood and character changes are dizzying but perfectly poised and balanced. They have a conversational quality that seems to tremble on the verge of articulate speech. It is often said that everything Mozart wrote was an opera, and indeed the dialogues between the first violin and viola in the slow movements, especially of the C major and G minor quintets, have all the intimacy, passion, and ecstasy of his greatest love-duets.

OPPOSITES ATTRACT
The quintets in C major, K. 515 and G minor, K. 516 are each other’s opposite; some scholars have suggested that, like the C major and G minor symphonies, they reflect the duality of light and darkness in Mozart’s nature: the C major is bright and triumphant, suffused by radiant sunshine; the G minor plumbs the depth of loneliness, desolation, and despair.

From the first ascending arpeggio, the C major is all upward-striving affirmation; the themes in the G minor tend downward, diatonically and sequentially.

The C major smiles with carefree, joyful serenity; the G minor seems to sigh and sob in anguish. Its intense, lamentatious slow third movement is followed by an even slower introduction to the finale that contains some of the most grief-stricken music ever written: under a mournful, disconsolate melody, its cello pizzicati and sighing accompanying figures are like teardrops falling on the heart.

The finale itself is not only a surprise but a jolt: a cheerful, G major romp in rollicking 6/8 time that seems strangely light-weight for the rest of the piece. However, there are earlier hints that Mozart cannot bear the unrelieved hopelessness: the Minuet is defiant, with slashing, off-beat chords, and the Trio, based on the same motive but in major, comes as a balm of consolation. Together, these two works encompass an entire emotional world, plunging into the deepest abyss and rising to celestial heights.

The second pair of quintets, K. 593 in D major and K. 614 in E-flat major, is quite different. One theory holds that Mozart wrote them without external incentive, entirely to please himself; another claims that they were commissioned by the Hungarian merchant Johann Tost, dedicatee of two series of Haydn quartets. Both theories are credible: Tost, an excellent violinist, had recently come into some money and it is tempting to believe that Mozart was well paid for these exquisite works. On the other hand, the thought of this harried genius, constantly beset by the need to compose for money, carving out time and leisure to follow his inspiration simply for his own gratification, is also infinitely appealing.

For these two quintets are true masterpieces, crafted with meticulous care and unparalleled in their technical and structural perfection. The polyphony is so dense and complex that it can produce startling dissonances and cross-rhythms. For example, in the slow movement of the D major, the players may sometimes wonder whether they are together. Both quintets bubble over with high spirits, wit, and playfulness, but have contrasting slow movements: the D major’s is deeply serious and in part quite tragic, the E-flat’s has a courtly elegance.

There are two versions of the opening theme of the D major finale, leading to an unsettled controversy about “authenticity.” The eminent musicologist Alfred Einstein believes that Mozart originally wrote a descending chromatic line, but that by simply re-arranging the notes he gave it more “grace and character with a single stroke.”

Both quintets carry allusions to earlier works: the D major begins with a slow introduction whose opening cello figure recalls the B minor Adagio for piano, and there are numerous echoes of the string quartets. The reason these delightful pieces are played relatively rarely lies in their extraordinary technical difficulty; there are fast passages in the E-flat that must have been dictated by Mozart the pianist: they are almost unplayable on the violin. These are compositions for the connoisseur; they are hardly recommendable for informal sight-reading sessions. They more than repay careful study; time and patience will reveal their hidden treasures and deepen the enjoyment of their beguiling beauty.