Imagine a beautiful rose, highly perfumed, the first petal about to fall as it starts to pass its glorious peak, and you have something of the mood of this delicious program. Barbara Hannigan, who makes modern music sound so easy, and her regular piano partner, Reinbert de Leeuw—another committed modernist—take us into the world that produced Mahler, Klimt, Freud, and so many other great minds in Vienna at the turn of the 20th century. Harmony starts to decay in the music of Schoenberg, Berg—a near-perfect Sieben frühe Lieder—and Webern, while Wolf, Zemlinsky, and Alma Mahler give us German song in rich colors.