Pierre Boulez conducts Gustav Mahler’s Adagio from Symphony No. 10 in F-Sharp Major and “Des Knaben Wunderhorn” (“The Youth’s Magic Horn”), Songs for Voice and Orchestra, with soloists Magdalena Kožená, mezzo-soprano, and baritone Christian Gerhaher. The concert opens with the romantic and melancholy Adagio and continues with the songs, based on texts from a collection of German folk poetry.