A Testament of Greatness

New documentary of Birgit Nilsson reminds us of what we had—and can still treasure I’ve spent most of my life believing that Birgit Nilsson was the greatest Wagnerian soprano of my lifetime. A 2018 Unitel DVD, “Birgit Nilsson: A League of Her Own,” (distributed by Naxos), gives ample evidence to even make the argument she…