Exotic vocal

Not mainstream, not expected as per Western cultural standards, my guess... As when Debussy infused Eastern tunes into Western mainstream 100+ years ago. Not that easy to define nowadays that we r all mixed and racially-"corrected" but some genetic/racial knowledge tells us what that is.
like for me, Tchaikovsky's 4th under Karajan sounds "exotic": the guy never heard Russian folk tune "the birch in the meadow" so his take is beautiful but "exotic" to my ears. 

Lisa Gerrard, Yma Sumak, Cocteau Twins, you guys beat me to my all-time favorites (it is totally sick how many copies of original pressings LPs, 180g LPs, Japanese mini-LP CDs, SACDs copies I collected but not listening to...).
Since Bjork had been mentioned, let me add "Miranda Sex Garden": not exactly EXOTIC singers/dancers but beautiful Goth-oriented Bjork for all of us.
To move this thread off dead-serious Opera/Mid-Eastern direction, let me add Lene Nystrøm, the lead singer for Aqua: She sounds like a chipmunk on my fav "barbie" tunes, but, unfortunately, her ego got a shot and she decided to go mainstreem, Abba-style and she got Aqua disbanded.