If you consider that I was weaned on Black Sabbath & Tull, love uk Prog/pysch & Freakbeat, listen to late 70's/80's Roots & Dub reggae, am fond of Trance and House, and listen to all sorts of stuff inbetween, there's loads of stuff that I consider "essential"..
There is one artist that I listen to constantly ( at least 2/3 times a week, since 1995 when I first heard Mask & Mirror..), who's music is never far from the Cdp, or Ipod.
Loreena McKennitt. Canadian Singer/songwriter, who's earlier albums are grounded in folk, and who gets progressively more celtic/new age over the releases..
Absolutely beautiful voice, with no studio trickery, She sings live, as well as she records..
sounds trite I know, but I simply never get tired of hearing her voice....
you can get soundbites etc from:- http://www.quinlanroad.com