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

Another +1 on Alison Krause

Emmy Lou Harris

Sheryl Crow's duets are very soulful

Permission in advance to laugh

Janis Joplin, listen to the song Try - she's all in

Patsy Cline, a true natural and sounds so effortless

Etta James

Whitney Houston

Aretha Franklin the original diva

Kate Bush - The Hounds of Love!

Cyrille Aimee…Live At Smalls album

Petra Haden…her version of Shenandoah on the new recording from the jazz group Rope

Eva Cassidy…almost any recording 

I suggest you try "Calypso Blues" by Youn Sun Nah. It's just female vocal and upright bass.

If she has not been mentioned…Laura Nyro. 
Enjoy.