Define hard/easy to memorize? ...
in the meantime, this one comes immediately to mind. I have this score and recording. Superb.
Lee Hoiby - Schubert Variations for piano Op. 35a (composed 1979) - approx. 14 minutes (I might stretch it to 16 to really enjoy some of those juicy slower lyrical variations)
"The Hoiby variations began life 34 years ago as a solo piano piece derived from the third of Schubert’s German Dances, D. 336; they were finished in 1979. ...The variations move progressively away from the Schubertian outline, some retaining only the barest melodic or harmonic suggestion of the original. Yet the plaintive, bittersweet mood of Schubert’s laendler is seldom absent. A quiet lyricism predominates, occasionally broken by fast rhythmic activity: ...The soft reprise of the laendler theme makes a poignant coda, as if Hoiby, having created a modern homage to Schubert, were respectfully returning the music to its German roots. In all respects, it is a lovely, cannily crafted piece, one that will surely be given the wide exposure it deserves.
John von Rhein, Chicago Tribune,8/7/1984
…a set of variations on a strange and melancholy Schubert ländler, variations that draw further and further away from the theme before wonderfully returning to it in the pensive and beautiful ending. A couple of the lyrical variations are very pretty – the central one has an endless emlody loating over prismatically shifting chords – and the more outgoing ones are laid out over the keyboard inventively and attractively.
Richard Dyer, The Boston Globe
…a wonderful set of variations by Hoiby on a Schubert waltz. The music moves in a manner that at first flows naturally from the dark minor key of the waltz, and then flowers into some elegant and dazzling variations that are logical extensions of the Schubert original.
Paul Hume, WGMS Washington