The magnificent and disturbing C major quartet is the crowning point of Mozart’s six "Haydn" quartets. The work is true evidence of Mozart’s triumph in emulating Haydn in his Op. 33 collection of quartets from 1782, and achieving a balance of structure, musical style, and emotion. Mozart began work on the six quartets not long after moving from Salzburg to Vienna. It was then that he began to hear music by Bach and Handel on a regular basis at weekly gatherings in the Vienna home of Baron van Swieten. The power of contrapuntal writing began to have a deep and increasing effect on Mozart’s own part-writing at the time. The effect is at its most acute in the unsettling dissonances of the opening 22 measures of the C major Quartet. They give the work a nickname ("Dissonance") and arise from a synthesis of free counterpoint and chromatic, "highly spiced" harmonies, to use a term that was often thrown at the mature Mozart. The dissonances are calculated to shock—so much so that people at first accused Mozart of releasing the printed music without having carefully proofed the parts! Even half a century later, Belgian music theorist François-Joseph Fétis proposed a "fix" to Mozart’s strident harmonies by moving the first violin entry one beat earlier. Many applauded the idea; few went along with it. Today were the opening to be played with this crass insensitivity to Mozart’s boldness, it’s certain that the stone statue of the Don Giovanni Commendatore would appear on stage to sort things out. The suspense and tension created by the dissonance is released in the ensuing Allegro. The profound, aching Andante cantabile is one of the most sublime movements Mozart wrote. Throughout the chromatic minuet and serene finale, the musical invention and disciplined working-out of short motifs are exemplary. 

The beginning maestoso chorale appears simple, but it is incredibly ambitious, offering the listener the most basic form of four-part writing that every student learns, as if to say, this quartet will contain everything. It is also an affirmation, as is what follows. Beethoven, though often considered the Classical to Romantic bridge, wanted to reclaim his classically inclined aesthetic in this period. An oversimplified tenet for the Romantics is that content dictates form. For Beethoven, form was a primary driver in the creation of his best writing. Commentary often focuses on the radicalism of the late quartets, and of course they are radical, but the paradox is that their originality emerges from Beethoven’s impulse toward conservatism, a retreat from certain contemporary trends to expand and loosen formal constraints. In this quartet, the retreat is toward Bach, Handel, and the baroque, with an emphasis on contrapuntal writing and heightened clarity of form.

The quartet promptly gets on with the business of restless counterpoint. In the context of the maestoso, each new theme sounds as if it has been gathered from a disassembled chorale and scattered across the Haydn-esque sonata allegro form. Typical of Beethoven’s late quartets, shifts are abrupt, and transitions are unceremonious, creating moments of comprehensive disintegration and unease in preparation for resolution.

The second movement is a theme and variations, a form Beethoven was somewhat obsessed with in his late period. The six variations, unlike some of Beethoven’s related works from this period, do not reach for higher and higher levels of virtuosity, but simply and steadily unearth the inherent depth of one of the most beautiful melodies the composer ever wrote.

The buzzing scherzo contains the most intricate contrapuntal writing of the piece. It is a masterclass in anticipation and deception - just when a phrase feels that it is settling in, it will stop abruptly, or a unison shout will compel it to a new section.

The final movement does not reconvene themes from the previous movements as is often the case, but introduces two fresh themes, a flowing melody whose shape is reminiscent of the first theme of the piece, and a joyous march that propels with its decisive articulation and wide-open harmonic accompaniment. The great pleasure of this movement is its ending, a contrasting coda in a shifted key and meter announced suddenly by a violin trill, the same technique that brought the quartet out of the maestoso at the start. It is Beethoven’s classicism shining through clarity and unity, from beginning to end.