A late Romantic character piece that relies on expressive melody and chromatic harmony. It is representative of the minor-composer output that populated salon literature in the early 20th century.
The player must cultivate a deep, resonant tone to convey the work's inherent nostalgia.
Comparable difficulty and character — good candidates for what to learn next.
21 de Diciembre (Op.77) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 5.
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 21 de Diciembre (Op.77) lasts about 5 minutes.
21 de Diciembre (Op.77) 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 Body and Soul by Johnny Green, Fantasy in D minor by Wolfgang Amadeus Mozart, Prelude in E minor, No. 4 by Frédéric Chopin — see the full similar-pieces list on this page.