It's been difficult finding slow-tempo prog with a woman on vocals. Nothing like a long piece (although I love a condensed Curved Air song just as much), the sound of an electric piano, and letting the music breathe a bit. A change, something different, and something necessary at night when it's dark and I want to listen to music while I sit on my couch.

I've heard enough non-prog that fits this category and a bit burnt out on it, and while looking through filters and then perusing The Canterbury Scene, found some Cros that fits the criteria, but not for very long, as I continue listening.

^ definitely not a 70s band.. I don't know how much more clearer I could have been.

Electronic System - Sky Lab

https://www.youtube.com/watch?v=CDDEQM5lgvw" rel="nofollow - Ruphus - Into View / Inner Voice / Too Late / No Deal / Left Behind - Live 1977 (Remastered) - YouTube

Cortex - Tropeau Bleu. The whole album is superchill fusion with lovely jazz-vocals (mostly wordless but not all). Little like a less busy Cos (whom also qualify with ca. 1/3rd of their material).

But really, how about Return to Forever - Light as a Feather? Seems a pretty obvious suggestion. And Chick Corea - Return to Forever as Well.

You could also try the undeservedly obscure jazz flutist/singer/composer Kathryn Moses. She only sings occasionally, but when she does it's lovely (her second album, Music in My Heart is also worth checking out):

I have a little bit of Chick Corea and Return to Forever, who's song "Hello Again" fits, except a guy is singing, lol..

I just listened to Cortex - Tropeau Bleu.... Very, very nice. Thank you! I'll check out Kathryn Moses after I peruse some more Cortex.

I liked the first album, but the second the drums come in, it's quite active and not slow-tempo at all, but I'll YouTube Flora Purim, and saw on Wikipedia she's guested on a lot of things.

I love her vocals on the song "Return to Forever" - the vocables, which is another great sing about 70s prog-rock -- melodies and singing wonderfully without words as an instrument ala Clare Torrey on "The Great Gig In The Sky"..

I know the cover is a guy, but there's only a woman on vocals and you can start hearing this angel at 1:48.

not the biggest fan of the vocal belting in The Great Gig in the Sky... but I generally agree with the wordless vocals comment. I've got tons of jazzy wordless singing from 1970's Soundtracks and Library Music albums. I've tried to find every score featuring the wonderful Edda Dell'Orso. But that's rarely full albums of her on every track, and often she's just featured on a couple of songs. Primavera feature Edda on all the song though (the first ten seconds is an annoying intro that's not part of the actual track), so try and find it if you enjoy this. 

And this is a compilation I got from various soundtracks (featuring jazzy scats, plenty of sensual singing, some plain lovely, others with a lot of suspense etc... all magnificent)

-the timestamps here are useless, but I discovered this song here. Absolute perfection imo:

-anyway, if you're only looking for album reccomendations where all songs are exactly like you want it, you're gonna miss out on a lot of great and relevant music. Nothing I've heard by Flora Purim outside of RTF/Corea comes close as far as I know. Her voice is nothing spectacular really, but it's just the perfect fit for those two albums.

Empire - Mark I

There are more parts of slow, jazzy (chords and the great jazzy solo/noodling by Peter Banks) than there is aggressive parts, which I think is only on the track where Phil Collins plays, but it's not that aggressive and the tempo is never that fast.

Thanks for reminding me about Empire - I vaguely remember hearing about them back in the day but seeing as their recordings weren't released until around 20 years later they had slipped under my radar... till now that is.

A great find.