Michael Danna and Tim Clement, Canada 1977 (no download)

Although this duo released a few albums, I believe this is the only bone fide progressive work, and it's really a beauty, recalling Genesis and all the other greats of symphonic progressive like the softer, gentler Italian albums (e.g. Paese dei Balocchi), or, at times, the gorgeous French artists Didier Bonin who so skilfully combined electric guitar plus electronics in a very moody atmospheric whole.  There is a little mellotron here and there, which is always, always a one-way ticket to heaven.  Sometimes a female vocalist sings on top of gentle acoustic guitar plus chamber instruments (faked on keyboard I think), reminding me of the beautiful German album Hoelderlin's Traum or you could even say parts of the Comus LP (I mean the first masterpiece one obviously).

People Left Behind:

You can also listen to all the song samples on apple, here which is what I did.

No download, out of respect for the artists.
Note that you can purchase it digitally from the apple store, or, like me, buy the physical CD from the production company, which is presumably the artists themselves:
http://www.oasisproductions.com/music.html