When in 1780 Haydn sent the C-minor Sonata (which he had written almost a decade earlier) to the Viennese publishing house Artaria, he described the work as “the longest and most difficult” of his keyboard sonatas. Rather than counting measures, we can accept the composer’s word on length; as for most difficult, performers would need to be consulted.
The keyboard works of Haydn, like all the vast amount of music he composed, reveal a gradual, deliberate, craftsmanly development over the course of his long career. The earliest pieces, written either for clavichord or harpsichord, were not even called sonatas, but rather, in the Baroque manner, designated as partitas or divertimentos. (Remember that Haydn was born in the high Baroque; he was 18 when Bach died.) When his real sonatas began to appear in the 1770s, one begins to find some of them showing the expressive and dramatic style of C. P. E. Bach (the second son of Johann Sebastian). This style, known by the picturesque name Sturm und Drang (Storm and stress), was for Haydn a temporary but extremely important communicative element.
The C-minor Sonata is tangible, urgent proof, a kind of acknowledgment, if you will, of the influence C.P.E.’s dramatic, storm and stress expressiveness had on Haydn. The main theme strikes a tone of cool emotionalism, first in thirds, then sixths, then descending half steps. The connotation of the minor key is clearly evident in the seriousness of this main section as contrasted to the spirited secondary theme in major (C minor’s relative — E-flat major).
The first and last movements are in typical three-part sonata form; the middle movement is in two part song form, an Andante with a contrasting section using expressive syncopations.