Billy's Prayer by Alba Rosa Viëtor is a lyrical work that draws on late-Romantic harmonic colors. It is distinct for its introspective mood and the use of lush, sustained chords in the middle register.
Develop a warm, singing tone and use careful pedaling to connect the shifts in harmonic resonance.
Comparable difficulty and character — good candidates for what to learn next.
Billy's Prayer is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 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 Billy's Prayer lasts about 4 minutes.
Billy's Prayer 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 Ave Maria d'Arcadelt by Franz Liszt, Ave Verum Corpus de Mozart by Franz Liszt, Albumblatt by Johannes Brahms — see the full similar-pieces list on this page.