This piece is a highly virtuosic and complex work by the British-Indian composer Kaikhosru Shapurji Sorabji. It is distinguished by its dense harmonic language and massive technical demands typical of the composer's late-Romantic, Modernist style.
At Henle 9 this is among the most demanding works in the piano literature. The main demands: big chords that need weight without harshness; wide stretches that reward larger hands and clever redistribution; and fast passage work that stays light and even at tempo.
Beyond that, expect several simultaneous layers, each needing its own dynamic level, and chord voicing — bringing out one note inside a handful of others.
At roughly 12 minutes, stamina and memory become part of the challenge — plan practice in sections.
The primary challenge is navigating the dense, multi-layered textures and extreme harmonic shifts requiring advanced hand-span capability.
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.
Fantaisie Espagnole, KSS 19 is rated Henle level 9 of 9 — virtuoso repertoire, roughly concert / virtuoso level. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 9 — meaning you can already play level 8–9 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 Fantaisie Espagnole, KSS 19 lasts about 12 minutes.
Fantaisie Espagnole, KSS 19 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 Fantaisie Espagnole by Kaikhosru Shapurji Sorabji, Gaspard de la nuit by Maurice Ravel, Fandango, R.146 by Antonio Soler — see the full similar-pieces list on this page.