Mozart - String Quartet No. 19 in C Major 'Dissonant'

Two of the greatest composers of the classical music era happened to be good friends. Although there was 24 years difference between Mozart and the older Haydn, they came to know and respect one another during the winter months that Haydn spent in Vienna. There are many anecdotes concerning the two and their genuine affection and respect for one another.  As for Mozart's thoughts on Haydn, the following is an example:

At a private party a new work of Joseph Haydn was being performed. Besides Mozart there were a number of other musicians present, among them a certain man who was never known to praise anyone but himself. He was standing next to Mozart and found fault with one thing after another. For a while Mozart listened patiently; when he could bear it no longer and the fault-finder once more conceitedly declared: "I would not have done that", Mozart retorted: "Neither would I but do you know why? Because neither of us could have thought of anything so appropriate."

Joseph Haydn 

As for Haydn's opinion of Mozart, he told Mozart's father Leopold the following:

"Before God and as an honest man I tell you that your son is the greatest composer known to me either in person or by name; he has taste, and, furthermore, the most profound knowledge of composition."

It was Haydn's influence that set Mozart to writing string quartets, with an excellent set of six quartets published in 1785 and dedicated to Haydn. Quartet No. 19 in C Major was the last one in this set.

I. Adagio - Allegro - The first movement of this quartet begins with a slow introduction. It was this slow introduction with its daring (for the time at least) harmonies that led to the nickname 'dissonant'. It's been said that some music dealers returned the manuscripts to the publisher because they thought these harmonies were mistakes, and that a Hungarian nobleman got so angry over the supposed mistakes that he tore up the music. Even Haydn was initially shocked by the dissonance, but his faith in his friend didn't waver. He eventually defended his friend by saying, "Well, if Mozart wrote it, he must have meant it.”  Mozart's dissonant introduction stands in stark contrast to the music of the rest of the movement.

II. Andante cantabile - This movement is in sonatina form, which is sonata form without the development section.

III. Menuetto, Allegro - An elegant minuet in the home key of C major with a contrasting trio section in the  parallel key of C minor.

IV. Allegro molto - Written in sonata form, this music returns to the mood of the first movement.