Most unusual/mesmerizing female voice.

Silvana Ida of Apoteosi, 1975
Annie Haslam of Renaissance II, 1972

are angels

Jane Duboc of Bacamarte, 1983
Jane Relf of Renaissance I, 1969

Rocker:
Inga Rumpf of Frumpy & Atlantic,1970

Good hit on Yma Sumak!
I’ll add:
Diamanda Galas
Nina Hagen
Anita O’Day
Gretchen Parlato
Guesch Patti
Julee Cruz

Teresa Salgueiro;
Lisa Ekdahl;
Cat Power;
Feist;
Whitney Houston;
Beth Gibbons;
Carla Bruni;
Sky Edwards;
Dani Klein;
Ana Moura;
... ... ...

Big Mama Thornton, Wanda Jackson, Victoria Williams, Lene Lovich, Kate Bush, Loretta Lynn, Iris Dement, Aretha Franklin.

Patricia Barber......how does she hit those high notes?
Joan Baez........HAVE to give her a nod.
Edie Brickell.....always enjoy her.
Tori Amos..........Yup!
Natalie Merchant........have to second that vote!
Janis Ian.......don't know about unusual but can she sing!
Kate Bush.........gotta love her voice.
Sandy Denny.........A big hats off to the only female vocalist to accompany Robert Plant!