The present Sonata, a product of the year 1787 and Mozart's next-to-last sonata for the keyboard/string duo, was a close contemporary of the opera Don Giovanni, which places it in very good company indeed. That the composer could conceive a major operatic masterwork and a small chamber piece during the same period is further proof, if any were needed, of the incredible range of this superman's genius.

The Sonata owes its existence to no known impetus, neither a commission nor a request from a friend or performer. In light of the brilliance of the Sonata's piano part, however, there is reason to suspect that Mozart had himself in mind when writing the work. Not that there isn't a high level of equality in the work between the violin and keyboard; but, particularly in the first movement, the piano is downright brilliant, with more than just a few showoff passages. The very opening of the work suggests an emphasis on the keyboard, as it presents the single-line, subtly syncopated main theme with the violin shadowing it harmonically a third below. The violin soon enough has its way with the main idea, with the supporting part going to the piano, and from that point on there is plenty of give and take between the instruments, although the piano does introduce the next two themes. This is not to say that Mozart has here reverted to the old piano-with-violin-accompaniment scheme, rather that the keyboard is given plenty of the spotlight - along with the violin.

The middle movement Andante is the ardent heart of the work, testimony to the unsentimental emotional depth of which Mozart was a master. According to musicologist Alfred Einstein, the movement "realizes such a balance between Soul and Art that it seems God Almighty has let stop all motion for one minute of eternity in order to allow all Righteous ones to enjoy the bitter sweetness of life." This prose, if somewhat over-ripe, does indeed capture the essence of music that transcends the physical limits of two basically unlike instruments.

Following such elevated expressiveness, there is only one direction for Mozart to take - a rondo of surpassing ebullience. It has been pointed out that the rondo theme comes from a sonata of C. F. Abel (1723-1787), a composer the child Mozart had met and admired in London. This work, composed the year Abel died, suggests that the use of Abel's theme was a tribute to the memory of the composer. Mozart's way with the theme - there are also two other themes in the movement - is endlessly vital, creating a truly memorable finale to the Sonata.

Orrin Howard served for 20 years as the Philharmonic's Director of Publications and Archives.