In 1798 Ludwig van Beethoven thought the three trios he had just published as his Op. 9 were his best works to date. Since moving to Vienna in 1792, he had tackled both string and piano music in various combinations, and these trios were something of a culmination. Written for strings alone, they would not be mistaken as simply a vehicle for him as a pianist (Beethoven also played viola, though not as flashily), and they abandoned the serenade structure of two earlier string trios in favor of a leaner, more serious, four-movement form. Soon he would move on to writing his first string quartets, a riskier venture that demanded comparison to Haydn and Mozart. In the meantime, trios gave him a less scrutinized place to define what made him different.
The C-minor string trio is set in a significant key for Beethoven, the same one he later used for his Fifth Symphony. Like that symphony, the Trio begins with a striking effect: in this case, a rapid dynamic scoop from soft to loud, then snapping back to quiet for the opening theme. The opening movement is filled with quick contrasts and gestures that spike up in high relief. The slow movement turns to C major, but with a certain heaviness uncommon in the key. The Scherzo dashes darkly through unsettled rhythms, while the Finale Presto has an almost continuous flow, like a stream of loosely associated thoughts.