Mozart's early variations on the Dutch song 'Willem van Nassau' are a testament to his youthful compositional energy. They showcase a bright, engaging melody and offer a variety of inventive figurations.
Developing quick fingerwork and a light touch is essential for these variations.
7 Variations on "Willem van Nassau" (K.25) is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 4.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 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 7 Variations on "Willem van Nassau" (K.25) lasts about 6 minutes.
7 Variations on "Willem van Nassau" (K.25) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.