This is a virtuosic piano transcription/paraphrase based on the famous Rossini aria, designed to showcase technical prowess through ornamentation and rapid passagework. It adheres to the tradition of 19th-century operatic showpieces.
At Henle 8 this is concert repertoire: professional-level technique is the entry ticket. The main demands: fast passage work that stays light and even at tempo; precise articulation — the difference between crisp and blurred is the piece; and sharp dynamic and character contrasts held together in one arc.
Beyond that, expect big chords that need weight without harshness.
The performer needs to maintain crisp, sparkling articulation to convey the character of the original aria amidst the virtuosic embellishments.
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.
Concert Fantasy on Largo al Factotum is rated Henle level 8 of 9 — concert repertoire, roughly diploma level.
You should be comfortable at Henle level 8 — meaning you can already play level 7–8 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 Concert Fantasy on Largo al Factotum lasts about 7 minutes.
Concert Fantasy on Largo al Factotum 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 Rhapsody in Blue (Solo Piano) by George Gershwin, Hungarian Rhapsody No. 2 in C-sharp minor by Franz Liszt, 'I Got Rhythm' Variations by George Gershwin — see the full similar-pieces list on this page.