This is a brief but deeply evocative work by Messiaen exploring his signature modes of limited transposition. It is unique for its quasi-liturgical stillness and complex, shimmering chordal voicings.
At Henle 7 this is a late-advanced work — the technical demands are serious and sustained. The main demands: chord voicing — bringing out one note inside a handful of others; careful pedaling — clarity depends on the foot as much as the fingers; and precise articulation — the difference between crisp and blurred is the piece.
Beyond that, expect several simultaneous layers, each needing its own dynamic level.
The main technical hurdle is balancing the dense harmonic clusters to bring out the intended melodic contours.
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.
Diptyque is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 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 Diptyque lasts about 5 minutes.
Diptyque 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 Berceuse élégiaque, BV 252a by Ferruccio Busoni, Berceuse for Piano, BV 252 by Ferruccio Busoni, Creation of the World, VL 6 by Mikalojus Konstantinas Čiurlionis — see the full similar-pieces list on this page.