Well I'm gonna try and do some female singers. Strangely it's easy for me to hear Downers as singers... even though as I said before I don't really consciously assign them voices when I read.
Anyway:
Lush is the chick from the
Dresden Dolls or
Gwen Stefani
Estelyn Telcontar is
Loreena McKennitt
Fea is
Anna Nalick
Bethberry is
Mama Cass (think Dream a Little Dream)
Pio is
Carole King
Child of the 7th Age is
June Carter or
Bonnie Raitt
JennyHallu is
Kelly Clarkson
Kath is
Charlotte Church
Valier is
Hilary Duff
Meela is
Amy Lee
Lalwende is
Norah Jones
Thinlomien is
Joss Stone
Wilwa is
Paula Abduhl 
Kitanna is
Sheryl Crow
Celuian is
Sarah McLaughlin