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

I might suggest Amanda McBroom. Has several albums on Sheffield, maybe other labels.  And also, just to perform the song she wrote, "The Rose," Bette Midler.

One of the most insanely badass albums I've been listening to lately is Cande y Paulo, it's mind blowing...  She is amazing... Honorable female vocal albums mention goes to London Grammar, Lake Street Dive, This is the Kit... All incredible female vocals that will change your life

And on the classical side, Get all four volumes of Wagner's Ring Cycle which features numerous very competent female vocalists.  Use the recordings of the Vienna Philharmonic under Solti.  They were recorded by Decca in the early 1960's if memory serves.  Available on vinyl and lesser quality on CD.  (no heat seeking missiles, I have both.)

Katie Melua 

+++1 for Eva Cassidy

I'm buying female to male records at about a 5-1 ratio. Kudos to the female artist for all the great music being put out. 

My recommendations in order based on your interests.

1: Agnes Obel (album Aventine) Danish singer from Berlin writes and plays. Classical, Neoclassical,  Jazz, Indie. Have on lp and yes its mastered wonderfully. 

2: Hindi Zahra (album Homeland) Moroccan, Jazz, Folk, Blues, World

3: Eilen Jewell (albums Sea of Tears / Queen of the Minor Key) Idaho lady Bluesy, Folk, Country, edgy

4: Khruangbin (album Live at Lincon Hall) actually a trio group but has some vocals leed by female artist. Mostly instrumental and very creative fun live recording. Classic soul, rock, psychedelic,  surf rock

5: Lp (Laura pergolizzi) (album Lost on You) NY gal  rock, alternative rock, touch of country/Midwest, modern style alternative unlike the 90s.  Great recording good mastering.  Unique vocals you will either really like or hate. But give it a chance it's takes a minute to digest her sound but once you do gets stuck in your head.  Try song Lost on you first. 

6: Lake Street Dive (rachael price) (song What I'm Doing Here). See her live performance of this song. It's amazing. I have the single, not crazy about her albums but this song is special and she kills it on the vocals. 

Hope something I recommended works out to you or others