Johann Krieger was a master of the North German organ and harpsichord style, and this fantasia features clear contrapuntal lines. It provides a quintessential example of Baroque keyboard clarity and 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; fine finger independence within the hand; and precise articulation — the difference between crisp and blurred is the piece.
Beyond that, expect ornaments that need to sound effortless, not squeezed in.
The player must maintain absolute consistency in touch and clean articulation throughout the polyphonic lines.
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.
Fantasia aus C 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 Fantasia aus C lasts about 3 minutes.
Fantasia aus C 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 13 Variations on 'Es war einmal ein alter Mann' by Ludwig van Beethoven, Fantaisie, OL 68 by Louis Couperin, Dulce et utile by Johann Baptist Cramer — see the full similar-pieces list on this page.