Mozart’s Andante con espressione, the second movement of Sonata No. 9 in D major, K. 311, centers on a gently decorated melody in G major. Its short phrases combine appoggiaturas, dotted rhythms, and small rising or falling figures. The left hand supports them with sustained notes, moving inner lines, and broken chords. As the movement continues, the melody returns with more ornamentation, and the final section becomes more active before settling into a very quiet ending.

The opening theme places the main tune in the right hand above a bass texture with notes held across moving accompaniment. Forte and piano markings distinguish brief answering gestures. The next phrase adds flowing left-hand sixteenths beneath a more sustained upper line. This opening portion is repeated with separate first and second endings, allowing the music to continue into a stronger transition on its second pass.

The following material includes chordal responses, small trills and turns, and upper phrases that mix regular subdivisions with triplets. The accompaniment moves steadily underneath, sometimes with a held note continuing inside the pattern. A long right-hand trill stretches across changing left-hand chords, temporarily replacing the moving melody with a sustained ornamental sound. The closing gestures alternate stronger and quieter statements and include wider intervals in the upper voice.

The main melody returns with additional decoration. Small-note figures fill in some of its familiar shapes, while the lower line also becomes more elaborate. Short detached chords still punctuate the phrases, preserving the movement’s conversational rhythm. The secondary material follows in a varied form, with ornamented upper notes over continuous left-hand sixteenths and occasional notes sustained within that accompaniment.

On the final page, another extended upper trill leads through changing lower chords and brief dynamic contrasts. A chromatic run guides the music toward a more decorated statement of the principal melody. The accompaniment then becomes quicker, with thirty-second-note broken figures beneath the upper line. Near the close, the right hand expands into octaves while the left hand alternates bass notes and repeated chords. A diminuendo and rallentando soften this activity into a pianissimo final cadence.

Interesting fact: The score shows both a literal repeat with alternative endings near the beginning and later written-out returns with changed ornaments. Those later passages are visibly different versions of the theme, not simply instructions to repeat the original notes.