I'll complete the list with most extra-ordinary female singers I've learned throughout my musical devotion...
Dimanda Galas often with Gothic appearance... Pure free spirit and mind
https://www.youtube.com/watch?v=P3ROtXm-dbYMeridith Monk mixes minimal piano with incredible voice improvisations
https://www.youtube.com/watch?v=SSf0FmXB_6MLHasa De Sela -- French Canadian born to Jewish mother and Mexican dad chosen to perform gypsy songs in Spanish with incredibly deep voice. Unfortunately she did not live long life and did not create enough work to enjoy her. This is one of her last performances before terminal disease took away her life... If you won't get goose bumps and chills on your skin, than there's something you miss
https://www.youtube.com/watch?v=2-Y_4tW0jnwAnd finally (can you consider that exotic?) Nina Hagen -- mother of Punk. Many of us know her huge voice range from low male tenor to coloratura soprano... I enjoy this one of my favorite her late 70's video
https://www.youtube.com/watch?v=7-FMglTIO30