This is a 20th-century work that blurs the lines between a traditional sonata structure and a freer fantasy. It is notable for its eclectic harmonic language and unconventional development sections.
At Henle 4 this is an intermediate piece that expects secure technique and real attention to phrasing. The main demands: a true singing tone, with the melody floating above the accompaniment; careful pedaling — clarity depends on the foot as much as the fingers; and sharp dynamic and character contrasts held together in one arc.
The main challenge is balancing the contrasting structural sections to maintain a cohesive narrative arc.
Comparable difficulty and character — good candidates for what to learn next.
A level or two down with the same spirit — ideal if this piece is still out of reach.
Where this piece's skills lead: slightly harder works making similar technical demands.
Fantasia Sonata is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 Fantasia Sonata lasts about 6 minutes.
Fantasia Sonata is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.
Pieces at a comparable difficulty and character include Fantasia by Melvin Clive Bird, Eros by Melvin Clive Bird, Die Zelle im Nonnenwerth by Franz Liszt — see the full similar-pieces list on this page.