I was chatting with dear friend Bocca L. Lupo (aka Bucky) and dear Birgit Nilsson came up in conversation, as he was listening to a recording of early excerpts from Nilsson's career. So I immediately hied me to YouTube to listen to recordings I'd found and loved so many times before, and I found this very interesting episode of Opera News on the Air from 1963. Nilsson and Joan Sutherland discuss and demonstrate vocal terminology.
Oh, the quotes from this clip! "That's very true, Birgit dear..."