(In this context, Boulez had expressed admiration for the third piece of Schoenberg's Three Piano Pieces, Opus 11, as well as for the piano part in the "Die Kreuze" movement of Pierrot lunaire.)
Boulez was impressed by Schoenberg's Third Piano Piece, Opus 11, and the piano part within the "Die Kreuze" movement of Pierrot Lunaire.