Most unusual/mesmerizing female voice.


Natalie Merchant gets my #1 vote!
slaw
That would be Sussan Deyhim. Try Madman of God album, her best.
This is not your Loreena, Ella, El.Frazer, Lisa Gerard etc. This comes from a very different culture.
Take a listen to Concha Buika, the queen of flamenco fusion. Check out "La noche más larga" and "El Último Trago" with  the great Chucho Valdes on piano. I also consider Cecile Mclorin Salvant on her debut album up there with the greats.
Kelly Flint from "Dave's True Story" fits the "mesmerizing" category which most posters seem to emphasize over "unusual".  When combining unusual with mesmerizing, I can't believe that in 6 years and 114 posts that no has mentioned Patricia Barber!  LUDITES! (LOL)