Exotic vocal

Sade.

Nah, Sade's voice is thin and superficial. She's got some of something but you have to guess it more than you can actually hear it.

Elizabeth Fraser of This Mortal Coil (and Cocteau Twins) ...
Song To The Siren
https://www.youtube.com/watch?v=HFWKJ2FUiAQ

Very different from all other versions.

Kathleen Ferrier (1912-1953), most notably as far as I am concerned in her 1947 recording of Brahms' Alto Rhapsody.

As someone said in a comment to the video:

This has to be one of the most beautiful and moving pieces in all of Western music.

Regards,
-- Al
 

The undisputed queen of the exotica genre is Yma Sumac from the 1950's when the genre was at it's apex. She was Peruvian-American and was famous for her extreme vocal range said to be well over 5 octaves. Check her out here hitting 4 1/2 octaves and singing in "double voice".