Widely known as the 'Raindrop' Prelude, this piece features a haunting, persistent repeated note that suggests falling rain. It is a study in atmosphere, juxtaposing a serene, songful melody with a dark, brooding middle section.
The performer must master subtle voicing to ensure the repeated 'raindrop' note does not overpower the delicate melodic line.
Comparable difficulty and character — good candidates for what to learn next.
Prelude in D-flat major, No. 15 is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 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 Prelude in D-flat major, No. 15 lasts about 6 minutes.
Prelude in D-flat major, No. 15 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 Nocturne in B-flat minor, No. 1 by Frédéric Chopin, Nocturne in E-flat major, No. 2 by Frédéric Chopin, Étude in E major, No. 3 by Frédéric Chopin — see the full similar-pieces list on this page.