i was kind of thinking about the venn diagram that my music collection would consist of...
vocal circle 1 - the quirky (hanne hukkelberg, stina nordenstam, jesca hoop, tunng)
vocal circle 2 - the ethereal/chanteuse (love spirals downwards, heather nova, tori amos, cocteau twins)
vocal circle 3 - the powerhouse vocalist (ella fitzgerald, oumou sangare, bessie smith, joantha brooke)
vocal circle 4 - the freak-folky (Tunng, Devendra Barnhart, Jana Hunter, Regina Spektor)

style 1 - the chill/downtempo/trip hop/electronic
style 2 - the straightforward singer songwriter
style 3 - uniquely arranged/experimental
style 4 - the world beat

anything with a more straightforward arrangement typically will have a singer that fits into at least 1, (if not more than 1) of the vocal circles