I see where you're coming from, but most of the tracks on Sarah McLachlan's "Surfacing" album are very much like that. It's a really fantastic album. Her "Fumbling Towards Ecstasy" album is another treat.
BTW, the song is just called "Angel"
Try some stuff by Beverly Craven, some nice piano tracks and great female vocals there too.
Also, you might like Anita Baker's "Sweet Love" (it's a song, not an album). Lovely mellowness (though there are drums) and great for late nights. Oh, pianos feature prominently too
Mary Beth is another superb artist. Beautifully mellow and lovely piano work. Sadly, her CDs are hard to obtain so I had to buy some from Amazon.com (which always costs more than I would've liked) and one out of print one from eBay in the US. But you can download some of her MP3s for free from here:
http://artists.mp3s.com/artists/260/...h_maziarz.html
(It's legal too because the record company put them there

).
Let me know what you think of them