Piano preludes 15 and 19 are now available as Acrobat scores. Number 15 is a pounding almost rock-like piece, exploring just how dissonant an almost white-note composition can be:
Piano Prelude 15 - Acrobat Score
Piano Prelude 15 - New Recording
Prelude 19 is more New Orleans-flavored, with a funky flair without being pounding.
Piano Prelude 19 - Acrobat Score
Piano Prelude 19 - New Recording