Wolfgang Amadeus Mozart (born 1756, died 1791) composed twenty-three (23) string quartets of ninety individual movements; a genre cemented by his mentor Franz Joseph Haydn after 1750 in Austria. Mozart wrote his first string quartet at the age of 14, and his last in 1790 at age 35, a year before his death. The string quartets were conceived in sets, and the first seven quartets written in Italy while touring as a virtuoso instrumentalist performing concerts. Mozart’s first string quartet, K.80, was written in a single evening at an inn on March 15, 1770, in Lodi, Italy. The next six quartets, K.155-160, were composed in a few months in 1772 in Milan, Italy, at the age of 16. Italian stylistic traits adopted within the “Milanese” quartets include three movement lengths per quartet and operatic type melodic emphasis featuring the soprano voice instrument (violin) while other instruments provide rhythmic and harmonic voice accompaniment predominantly. Three “Divertimenti” for string quartet, K.136-138 written in Salzburg in 1772, are titled as such on Mozart’s manuscript. The next set of six quartets, K.168-173, known as “Viennese” for the place they were written, were composed in late 1773 but not published until 1801, after Mozart’s death. While in Vienna Mozart incorporates Haydn’s idea of four movements, and includes a minuet/trio as the third movement. Mozart’s next set of six quartets – K.387, 421, 428, 458, 464 and 465 – were composed between 1782 and 1785 while in Vienna and dedicated to Franz Joseph Haydn, and known as the “Haydn” quartets. Published in 1785, Mozart stated in his written dedication: 

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“To my dear friend Haydn, 

A father who had resolved to send his children out into the great world took it to be his duty to confide them to the protection and guidance of a very celebrated Man, especially when the latter by good fortune was at the same time his best Friend. Here they are then, O great Man and dearest Friend, these six children of mine. They are, it is true, the fruit of a long and laborious endeavor, yet the hope inspired in me by several Friends that it may be at least partly compensated encourages me, and I flatter myself that this offspring will serve to afford me solace one day. You, yourself, dearest friend, told me of your satisfaction with them during your last Visit to this Capital. It is this indulgence above all which urges me to commend them to you and encourages me to hope that they will not seem to you altogether unworthy of your favour. May it therefore please you to receive them kindly and to be their Father, Guide and Friend! From this moment I resign to you all my rights in them, begging you however to look indulgently upon the defects which the partiality of a Father's eye may have concealed from me, and in spite of them to continue in your generous Friendship for him who so greatly values it, in expectation of which I am, with all of my Heart, my dearest Friend, your most Sincere Friend, W.A. Mozart.” 

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Mozart befriended Haydn in 1782 as they played music together, Mozart on viola and Haydn on violin. Mozart studied Haydn’s string quartets in great detail. Haydn first heard Mozart’s string quartets in 1785 at which point he stated:

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“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, what is more, the most profound knowledge of composition.”

Mozart’s K. 499 was written in 1786 in Vienna and published by a friend, Franz Anton Hoffmeister. The final set of string quartets composed by Wolfgang Amadeus Mozart, K.575, 589 and 590, were composed between 1789-1790 and dedicated to the King of Prussia. The “Prussian” quartets, similar to the “Haydn” quartets, treat all instruments equally in regard to melodic and rhythmic importance. Wiener Zeitung announced their publication in 1791 after Mozart’s death: 

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“... these quartets are one of the estimable works of the composer Mozart, who was torn untimely from this world; they flowed from the pen of this so great musical genius not long before his death, and they display all that musical interest in respect of Art, Beauty, and Taste, which must awaken pleasure and admiration not only in the amateur but the true connoisseur also.” Haydn commented further, “If Mozart had written nothing but his violin quartets and the Requiem, they alone would have been sufficient to make him immortal.”