Mozart’s Sonata No. 10 in C major, K. 330, begins with an Allegro moderato whose graceful upper melody is continually decorated by quick notes and trills. The left hand often supplies an even broken-chord accompaniment, while the right hand moves between dotted gestures, short slurs, and running figures. The music’s light surface contains frequent changes of texture and register. Two large repeated sections carry the movement through its opening ideas, a changing middle passage, and the return toward a compact final cadence.

The main theme begins with a dotted shape that falls through a small group of thirty-second notes. Trills and short rests give its answering phrases a distinct profile. Underneath, the left hand keeps a regular sixteenth-note pattern, generally quieter than the melody. Some passages add another moving voice within the right hand, so that quick upper notes sound above a line held or moving at a different pace. Rising flourishes and shorter detached figures alternate as the opening expands.

The secondary material introduces chromatic notes and more ornamental upper phrases over broken accompaniment. At several points, the left hand moves in groups of three while the right hand continues its own rhythm. Longer runs then give way to dotted notes, appoggiaturas, and small trills. The closing passages bring in upper double notes and figures that spread across different registers, with short responses from the bass. A repeat sign returns through this first large section.

The middle section changes the harmony while keeping much of the familiar accompaniment motion. The upper line breaks into shorter gestures, including notes placed between the main beats, quick decorative fragments, and phrases separated by rests. Crescendos and changes between forte, piano, and pianissimo distinguish these exchanges. The principal theme eventually returns with its dotted opening, falling flourish, and quiet left-hand pattern.

The later pages revisit the secondary ideas and triplet accompaniment, then expand the closing material with more upper double notes, trills, and quick runs. Near the end, the hands exchange brief decorative gestures and the upper line rises and falls through changing harmonies. A poco rallentando marking relaxes the final cadence. The repeat at the end sends the player back through the movement’s second large section.

Interesting fact: The printed metronome marking is eighth note equals 126. Because many of the decorative runs use thirty-second notes, recognizing that beat unit helps distinguish the steady underlying pace from the faster surface activity.