I like Jean Redpath for Scottish singing,
Jean Ritchie for American traditional,
Tish Hinojosa contemporary singersongwriter,
commercial bluegrass Alison Krauss.

Like Art's pick, from the 1950's, Mary O'Hara, from Sligo raised in the tradition, but had vocal training later... as Jean Ritchie would call it, Mary O'Hara had a "cut crystal" voice. It's not a pure folk sound, but still O'Hara is in kind of her own niche.

I like Mary Black, Sandy Denny, Maddy Prior, Dolores Keane, already mentioned,
and Jacqui McShee from PENTANGLE.

I like to listen to independent "unknown" singers and musicians on mp3.com, people who are making music at home and sharing it through the internet. Give a listen to the voice of Melissa Webb, bluegrass, Click here Not sure what you mean by pure, so I just listed some I enjoy and appreciate for what they can do. Most singers I listen to are on Irish or Scottish recordings.

Also give a listen to Jodee James, an American singer of Welsh songs Click here

AND our own Mudcatter Denise Couch, in England, who with her husband Ned make the duo MAD RUSH.Click here Denise "Deni" is a good songwriter, too.