This is a duplicate reference to the Ketterer Mazurka Op. 40, a quintessential salon work of the mid-19th century. It showcases the composer's focus on melodic charm and rhythmic accessibility rather than complex structural development.
At Henle 4 this is an intermediate piece that expects secure technique and real attention to phrasing. The main demands: rubato that must breathe naturally without losing the pulse; a waltz lilt that needs charm and a flexible left hand; and ornaments that need to sound effortless, not squeezed in.
Beyond that, expect a true singing tone, with the melody floating above the accompaniment, and a left hand with real melodic or rhythmic responsibility of its own.
Focus on the subtle rubato required to make the dance rhythm sound authentic rather than mechanical.
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.
Diamantine (Op.40) 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 Diamantine (Op.40) lasts about 4 minutes.
Diamantine (Op.40) 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 Diamantine, Mazurca Op.40 by Eugéne Ketterer, American Beauty by Joseph Francis Lamb, Berceuse by Rudolf Friml — see the full similar-pieces list on this page.