Not my genre wheelhouse so please don't tar and feather me since it's meant to be a compliment...  kinda got a little Mama Cass vibe from Sandy Denny.   Mind you all I know of Sandy is a tiny bit from the videos posted by gothic here.  British folk rock compared to American folk rock.
Watched a Janis Joplin Ball n Chain video the other day of her at Monterey with Mama Cass awestruck in the audience. Which somehow had me draw a connection between Mama and Sandy.
If you like a clean voice with piano, have you heard any Tori Amos?  Perhaps live at Montreux 1991/ 1992...  for example her song Winter.  Can post a link if you are interested.  A very talented lady.  Maybe not your cup of tea, but thought I would throw that out there.  Liked her a lot in the '90's.  
As Clegg liked to say 'I'll go stand over there and be quiet now.'