In spite of his numerous outstanding contributions to the symphonic genre, Mozart did not have the Haydn's desire to expand the form, nor Beethoven's commitment to maximize its effect. He wrote his final three symphonies (#39 in E-flat, K. 543; #40 in G minor, K. 550; and #41 in C, K. 551) during a six-week span in the summer of 1788. These three pieces surpass any of the composer's previous symphonies, and it would be reasonable to speculate that later efforts would have been even more impressive. But Mozart would not be inspired to try his hand at symphonic composition again, even while remaining prolific, completing 75 works during the final three years of his life. Furthermore, his reason for turning so intensely to the symphony during this month and a half is unknown, although some have suggested that the trilogy is a reaction to the loss of his father Leopold, who died in May 1787.
Little is known about the first performances of any of these final three symphonies; evidence seems to indicate that #40, at least, was performed in Mozart's lifetime, but the issue is less clear for either #39 or #41. Nonetheless, Mozart did seem to be writing the pieces with specific performances in mind: perhaps a loosely formed plan had encouraged him to devote time to the project, only later to fall through. The original version of the Symphony #40 does not have clarinets, but Mozart created the second version, with the clarinets, almost immediately afterward, possibly with a view toward a performance by a different organization. The clarinet sound is well suited to the overall dark atmosphere of this symphony, and the second version is more frequently performed today than the original.
The Symphony #40 has for two hundred years been a favorite among Mozart's works, probably due to its unusual degree of expression, foreshadowing the Romantic movement of the next generation of composers. Mozart wrote only one other symphony in a minor key, that being #25 (also in G minor), and minor-key symphonies by any composer were uncommon during the late Classical period. In this work, the expressive character is defined not so much by the choice of the minor key, but by the extreme harmonic poignancy and motivic dialog. Of particular interest are the development sections of the first and last movements: the development section of the finale, in particular, makes use of melodic skips and harmonic progressions that must have bewildered contemporary audiences. Given its position as arguably the finest example of 18th-century symphonic writing, the popularity of this work figures to survive far into the future.