Maureen Forrester, contralto.

The local "classical" music station is currently having an hour long program dedicated to the work of Maureen Forrester, the Canadian contralto, who rose from very humble beginnings to be a major force on the international concert and opera scene, and in latter life, as an arts administrator with the Canada Council.  This summer, to mark the anniversary of her death from Alzheimer's Disease last year, the Stratford Festival is holding what sounds like a wonderful tribute event to remember her:

http://www.stratfordsummermusic.ca/index.php?option=com_content&view=article&id=54&Itemid=55

Youtube has a few recordings, probably not the best, but they do give a sense of the power and beauty of her incredible voice.