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This duet is phenomenal. Never heard of Haley Reinhart before, but that is one of the most impressive and enchanting voices I've heard:

https://youtu.be/aVevvbFNKiY

Sarah Vaughan (both early and later years)
Audra Mae
Nathalie Stutzmann
Grace Love
Aurora
Silja Sol (often backing the above)
Sharon Jones

Honestly, Adele and Ariana Grande have phenomenal...