This Allegro is a robust and engaging movement from one of Mozart's piano sonatas, showcasing his characteristic clarity, grace, and melodic invention. It features rapid passagework and a sophisticated development of its themes.
Demands excellent finger dexterity and evenness in rapid scalar and arpeggiated passages.
Allegro (K.121) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 8.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Allegro (K.121) lasts about 5 minutes.
Allegro (K.121) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.