Female Vocalist like Diana Krall, Jacintha.

Not sure if she fits in with your description, but I think that Jennifer Warnes is very much under rated with a superb voice. Most will cite "Famous Blue Raincoat" as her definitive album. However, I personally think that "Shot Through the Heart" and "Hunter" are both superior albums in terms of content, if not sonics.

Try also try, Marlena Shaw "Live in Tokyo" on Eighty-Eights, a Japanese pressing, of you can find it. Maybe it is on CD, too, I don't know.

I like Eva Cassidy, as well. Also, Janis Ian "Between the Lines" and "Breaking Silence".

Have you tried Dinah Washington?

Ella Fitzgerald, simply the best.

Hpshps, I agree completely with Lizz Wright and would also suggest Orna and Jenna Mammina. You won't be disappointed.

Shirley Horn - The Original Diana Krall - anything by Shirley Horn...

Besides those mentioned,

Karrin Allyson - "In Blue" is a widely ranging mix of captivating soul jazz classics and ballads.

Jane Monheit - "Come Dream With Me" great standards with the best rendition of Over the Rainbow I have ever heard.

Both have magical qualities.