The first movement of Mozart’s Sonata No. 9 in D major, K. 311, is an Allegro con spirito that combines bright chordal gestures with quick, neatly shaped passagework. A strong opening chord is followed by a rest and a rising-and-falling right-hand figure. Detached notes, sudden changes between forte and piano, and moving accompaniment patterns keep the music lively. The movement develops several of these ideas before bringing the opening theme back prominently on the final page.

The opening section alternates compact statements with more continuous motion. The right hand moves between running sixteenths, short trills, and separated melodic notes, while the left hand changes from held intervals to broken chords and regular eighth-note patterns. Accents draw attention to the start of the longer upper runs. A quieter secondary idea, marked dolce, then places a more relaxed melody above a steadily moving bass.

The closing part of the exposition gives both hands substantial passagework. The right hand first carries continuous sixteenths over widely spaced lower notes. The left hand then takes over the rapid motion, using repeated broken-chord patterns beneath a melody with dotted rhythms and ornaments. Brief emphatic chords interrupt this activity, followed by a softer passage of slurred double notes. The printed repeat returns to the beginning before the development starts.

The development initially draws on those paired, slurred gestures rather than immediately restating the opening tune. Chromatic changes alter the harmony, and the right hand begins quick figures that alternate between octave positions. Below them, the left hand sometimes supplies a moving melodic line and sometimes holds intervals. The rapid figures later move into the lower hand. A brief poco ritardando interrupts the flow before an a tempo marking restores the earlier pace.

The later pages build through long upper sequences, stronger dynamics, and renewed secondary material. Much of the closing texture again places an ornamented right-hand melody above continuous left-hand sixteenths. On the final page, the opening chord-and-run theme returns in the passage labeled coda. More running notes and accented chords follow, but the last gestures become quieter, with paired slurs and a compact final cadence.

Interesting fact: In this score, the opening theme’s prominent late return is labeled as part of the coda. The secondary and closing ideas have already returned before this recognizable beginning reappears.