Mozart’s Sonata No. 5, K. 283, begins with an Allegro in G major and three-quarter time. Its light opening melody is supported by a steady moving accompaniment, but the texture soon expands into rapid runs, fuller chords, and exchanges between the hands. The first large section repeats before a contrasting middle passage and the return of the main themes. Frequent changes between smooth and detached playing give the movement a lively, conversational character.

Opening theme: A dotted pickup introduces the upper melody. Short slurred groups alternate with separate notes, while the left hand supplies a continuous eighth-note pattern. The phrase answers itself in a lower register before stronger chords and a quick run enlarge its range. The bass becomes more emphatic, and a flowing figure passes through the lower part of the keyboard before the next theme enters.

Secondary theme: A quieter melody unfolds over broken-chord accompaniment. Small ornaments and changes of touch decorate its outline. The upper line then becomes more active, with chromatic notes and quick changes of direction. Short chordal replies interrupt the running passages, and the left hand alternates between close-spaced patterns and more open bass support.

Closing section and repeat: Longer upper runs lead into trills and sustained inner notes. The moving line sometimes lies below a held melody note, creating two distinct layers within the right hand. Lower figures answer the upper ornaments, and a descending run prepares the final chordal gestures. The first repeat closes this extended opening section.

Middle section: The music resumes with short, lightly accompanied fragments. Offbeat chords and small ornaments give the phrases a different rhythmic profile. The left hand maintains repeated notes beneath fuller upper harmonies, then the texture becomes more mobile. Changing harmony and register lead back toward the opening idea.

Return and ending: The main theme returns with adjustments to its accompaniment and melodic route. The secondary material follows, bringing back the contrast between quiet melody and more brilliant running passages. The final page extends the closing material through trills, inner voices, and a moving bass. Short chordal statements complete the movement without a second large repeat.

Interesting fact: Near the first repeat, the score places moving notes underneath sustained upper notes, asking one hand to carry a held voice and a separate active line at the same time.