Martín Sánchez Allú was a Spanish virtuoso whose works were highly technically demanding for the time. This piece makes use of rapid arpeggiated figures and sudden mood changes to create a 'magnetic' tension.
At Henle 5 this is a late-intermediate piece — technically substantial, with musical demands to match. The main demands: sharp dynamic and character contrasts held together in one arc; sweeping arpeggio figures that must stay smooth across positions; and a left hand with real melodic or rhythmic responsibility of its own.
Control the wide-span arpeggiated left-hand accompaniments to avoid blurring the harmonic content.
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.
El sueño magnético (Op.38) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 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 El sueño magnético (Op.38) lasts about 5 minutes.
El sueño magnético (Op.38) 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 El jitano by Martín Sánchez Allú, El peregrino by Martín Sánchez Allú, El Ave enamorada by Martín Sánchez Allú — see the full similar-pieces list on this page.