These variations are a masterful display of Cabezón's ability to manipulate vocal-style themes into keyboard idiom. The writing is highly idiomatic for early keyboard, emphasizing polyphonic rigor.
At Henle 6 this is an advanced piece that assumes fluent technique and rewards mature interpretation. 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 achieve independence between the voices while balancing the historical performance practice of ornamentation.
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.
Diferencias sobre 'De quien teme enojo Isabel' is rated Henle level 6 of 9 — advanced repertoire, roughly ABRSM grades 7–8. In the RCM system it corresponds to about level 8.
You should be comfortable at Henle level 6 — meaning you can already play level 5–6 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 Diferencias sobre 'De quien teme enojo Isabel' lasts about 4 minutes.
Diferencias sobre 'De quien teme enojo Isabel' 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 Diferencias sobre 'La dama le demanda' by Antonio de Cabezón, Differencias sobre 'El Canto del Caballero' by Antonio de Cabezón, Diferencias sobre la gallarda milanesa by Antonio de Cabezón — see the full similar-pieces list on this page.