Most unusual/mesmerizing female voice.

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!

Adele
Live at Royal Albert Hall