Sonata movement in C major (fragment), K. 688

What Is Known

K. 688 is transmitted as an uncompleted sonata movement for clavier (keyboard) and violin in C major, and its authenticity is listed as verified in the Mozarteum’s Köchel Verzeichnis entry.[1] The same entry dates the fragment to Vienna, within the span 1783–22 April 1784; the precise day of composition is not specified.[1]

This conflicts with occasional database-style metadata that associates K. 688 with “vocal music” or “canons”—a mismatch with the work’s identification and classification as a piano-and-violin sonata movement. Given the Mozarteum catalogue’s explicit scoring and genre placement (“Duos with piano”), the sonata-fragment description is the firmer basis for understanding the piece.[1]

Musical Content

Because K. 688 survives only as a partial movement, it is best heard (and read) as a window into Mozart’s workshop rather than a complete formal statement. Even in fragmentary form, the designation “sonata movement” suggests a design oriented toward Classical sonata thinking—a thematic argument intended to unfold over a larger span than the page now preserves. In the Viennese years around 1784, Mozart’s keyboard-and-violin writing typically treats the violin as an increasingly articulate partner to the keyboard, and K. 688 likely belonged to that forward trajectory, even if its musical logic breaks off mid-course with the surviving material.[1]