Controversial Singers (????)

  I have selected some artists I feel belong in my "controversial" category. I love most of them,but some I never could grasp...that is the way of things in life. One person exits a film and raves;the other one is totally negative. Same with opera, so PLEASE do not send me too much hate mail, because after all, I am a fairly nice guy.
    The artists are:
        Martha Moedl, Leonie Rysanek, Theresa Stitch-Randall, Boris Christoff, Dietrich Fischer-Dieskau, Conchita Supervia, Lily Pons, Christina Deutekom, Ivan Koslovsky, Giovanni Martinelli, Maria Callas, Renata Scotto, Magda Olivero, and Leyla Gencer.
                                 (71 minutes)