In June of 1789 Mozart arrived home in Vienna from a trip to Berlin, during which he received a commission for six string quartets and a group of piano sonatas from the Prussian King, Frederick William II, nephew and successor of the immensely cultured Frederick the Great. Frederick William was an avid music lover and excellent cellist. Mozart immediately began composition and in July of 1789 completed the Quartet in D major (K. 575) and one of the piano sonatas (K. 576). The summer of 1789 was not an easy one. His health was poor, his finances worse, and his Constanze was now pregnant for the fifth time in seven years. He spent a great deal of time reviving his most wonderful opera, The Marriage of Figaro for the Emperor, Joseph II, for concerts at the end of August. The success of that production led to a new commission that resulted in his great ensemble opera, Cos� fan tutte.

That Christmas, Mozart undertook the composition of a chamber work for the Vienna Society of Musicians concert held every year to benefit the widows and orphans of its deceased members.

Anton Stadler, principal clarinetist of the Imperial Court Orchestra, was enlisted for the event and so Mozart composed a quintet for clarinet and strings. Stadler was a Freemason, and, when Mozart had joined the fraternity, the two musicians had become close friends. The work was completed on September 29, 1789 and performed by Stadler, Mozart (as violist) and three Society members between the two parts of Vinzenz Righini�s cantata, Apollo�s Birthday Festival, on December 22. Mozart and Stadler played the quintet again on April 9, 1790 at the Vienna residence of Count Johann Karl Hadik, Councilor to the Hungarian Exchequer and a gifted amateur painter, at which time the composer referred to it as "Stadler�s Quintet."

"If there is one work that sums up this unhappy year [of 1789], this must be it," wrote H.C. Robbins Landon of the Clarinet Quintet. "Parts of it seem to reflect an aching despair, but the whole is clothed not in some violent minor key, but in a radiant A major. The music smiles through tears."

Mozart harbored a special fondness for the graceful agility, liquid tone and ensemble amiability of the clarinet from the time that he first heard the instrument as a young boy during his tours. His greatest compositions for the instrument were inspired by the technical accomplishment and expressive playing of Stadler, for whom he wrote not only this Quintet, but also the Trio for Piano, Clarinet and Viola ("Kegelstatt," K. 498), the clarinet and basset horn parts in the vocal trios, the clarinet solos in the opera La Clemenza di Tito, the clarinets parts added to the second version of the G minor Symphony (K. 550), and the flawless Clarinet Concerto (K. 622), his last instrumental work, completed in October 1791, just two months before his death.

There were also a number of projected works for Stadler that Mozart did not finish: two fragments from 1787 for clarinet and string quartet (K. 516c and K. 516d); a piece for clarinet, basset clarinet (a slightly larger and deeper-toned instrument on which Anton�s younger brother, Johann, was an expert), violin, viola and cello (K. 580b), which immediately preceded the Quintet; and a movement (K. 581a) originally intended as the finale of the Quintet but reworked as Ferrando�s aria "Ah, lo veggio" in Cos�.