The jazz singer Cassandra Wilson performs at the Rose Theater at Lincoln Center in Manhattan on Sept. 30, 2011. With a self-possessed vision, Wilson married her easy and intimate tone to jazz, blues and folk experiments, opening the door to a new postmodernism. (Brian Harkin/The New York Times) By GIOVANNI RUSSONELLO There is a quality of almost holy slowness in Cassandra Wilson’s music that belies the speed and force with which it changed jazz history. Wilson’s was a voice that felt almost…
