Looking for good recordings of female vocals I have not yet tried...

Can toss Annie Lennox, Alicia Keys & Dianna Ross into the mix. All three very distinctive and certainly have their smokey/jazzy material. I too like Aimee Mann not so much for her voice but for her vibe and songwriting. Chaka Khan can punch it out with the best of them too. Some terrific Rufus LPs. 

Eliane Elias

Jane Monheit

+1 for Allison Krause and Cowboy Junkies

Add Secret Sisters, especially their first album.

Cecile McLorin Salvant 

One of the best..and very much alive.

Try "Dreams and Daggers"..well recorded live ...a Demo record for sure..

Margo Timmins ..another classic live recording with one stereo mike, "The Trinity Session"

but Cecile is in league with Ella and Billie..

Melody Gardot 👍