Louis Couperin's unmeasured preludes and fantasies represent the sophisticated French harpsichord style of the 17th century. This specific fantasy utilizes rigorous imitation and distinct motivic development.
At Henle 4 this is an intermediate piece that expects secure technique and real attention to phrasing. The main demands: independent voices that must each sing on their own line; ornaments that need to sound effortless, not squeezed in; and precise articulation — the difference between crisp and blurred is the piece.
Beyond that, expect fine finger independence within the hand.
The main challenge is maintaining rhythmic pulse through the ornate, non-metrical sections of the writing.
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.
Lesser-known works by the same hand, at a comparable level.
Fantaisie 'Duretez', OL 1 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 Fantaisie 'Duretez', OL 1 lasts about 3 minutes.
Fantaisie 'Duretez', OL 1 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 Fantaisie, OL 47 by Louis Couperin, Fantaisie, OL 27 by Louis Couperin, Fantaisie, OL 25 by Louis Couperin — see the full similar-pieces list on this page.