Most underrated female recording artists..

I'm always looking for female singers who make my 2 channel system seem worthwhile for all l have spent...the list includes Nora Jones, Diana Krall , Sade and many others.... there are some fabulous singers out there but not recorded very well...lm adding Bonnie Raitt to my top list..The Bonnie Raitt collection red book cd...tracks 16 and 17 are spectacular on my system...  I'f anyone could add a suggestion it would be appreciated..