I believe the woman is Hava Alberstein; she recorded the Hebrew version many years before Ephraim Buchwald rendered it into English. I also tend to think it was originally a Yiddish folk song, but I've never heard it in Yiddish.Shalom writes:
Quoting Krum as a Bagel, you wrote:
"Inevitably, the token Sefardi guy in the shul will be moved to sing "Ein Adir" in a ridiculously overdone nasal-y voice (etc.)"
You know what makes it even worse? Despite popular belief, "Ein Adir" isn't even of Sefardic origin to start with!
The composer of this piyut was Rabbi Yisroel Hapstein, better known as the Kozhnitzer Maggid. This doesn't sound like a Sefardi name to me...