Frederic Rzewski's De Profundis is a monumental work based on Oscar Wilde's prison letter, requiring the performer to speak, hum, and whistle while playing. It is a tour de force of avant-garde piano technique and theatrical performance.
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 sharp dynamic and character contrasts held together in one arc, and several simultaneous layers, each needing its own dynamic level.
At roughly 40 minutes, stamina and memory become part of the challenge — plan practice in sections.
The work requires extraordinary physical stamina and the ability to coordinate vocalization with complex percussive piano textures.
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.
Lesser-known works by the same hand, at a comparable level.
De Profundis 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 De Profundis lasts about 40 minutes.
De Profundis 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 Ballade No. 5 (It Makes a Long Time Man Feel Bad) by Frederic Rzewski, Ballade No.5 by Frederic Rzewski, Ballade No.6 by Frederic Rzewski — see the full similar-pieces list on this page.