First movement

Mozart described K. 545 in his catalogue as eine kleine Klaviersonate für Anfänger — a little keyboard sonata for beginners — and the description has stuck since 1788. The first movement is one of the most-played pages in the Classical repertoire: a clean Allegro in C major with two memorable themes, a brief development, and a recapitulation that begins (unusually for Mozart) in F major.

Technically the movement tests proper Mozartean Classical poise. The right hand carries the principal melody, a singing second theme, and bright running passagework; the left hand has Alberti-bass support throughout, with cadential figures at the section divisions. The technical priority is even passagework in the right hand and a steady, quiet Alberti pulse in the left — the texture is clear and unforgiving of unevenness.

Two pitfalls. First, the Alberti bass can become mechanical — Mozart's writing rewards a left hand that holds pulse but breathes with the melody, with a small dynamic curve under each phrase. Second, students often push the Allegro too fast and the running passages become unclear; build the tempo gradually with a metronome until each note speaks at the target speed.

Mozart's complete piano sonatas are on IMSLP in clean public-domain editions including the Neue Mozart-Ausgabe. Hearing the famous F-major recapitulation moment in context — and the Andante that follows — gives a complete sense of the sonata's architectural shape.