More contemporary jazz vocals you might enjoy -
Karrin Allyson - 'Collage' - Concord Jazz
" " - 'Ballads - Remembering John Coltrane' on Concord Jazz
Jeanie Bryson - 'Some Cats Know' (songs of Peggy Lee) TELARC
Laverne Butler - 'Blues in the City' - Max Jazz
" " - 'A Foolish Thing To Do' - Max Jazz
Shirley Horn - 'I Thought about you' - Verve
" " 'Close Enough for love' - Verve
Rene Marie - 'Live at Jazz Standard' - Max Jazz
Mary Stallings - 'Live at the Village Vanguard' - Max Jazz
Etta James -Mystery Lady- (Songs of Billy Holiday)
Etta Jones - 'Always in Our Hearts' - High Note. A memorial compilation of her music and an excellent introduction for those not familiar with her.
Good singers all. Try them
PS, re your request to boiling it down to 5.........My contribution - While I like all of those recommended I wouldn't be with out my collection of Shirley Horn. If you have never heard her, she was a model for Krall's style with the except that she has talent! Laid back, excellent piano playing, and her voice/phrasing is as good as it gets I think. Doesn't hurt that the recording quality is excellent as well.