There was a French group called Atoll in the '70's. I guess you'd label them "progressive rock," but it's nice stuff, not totally synthesizer or anything. Very cool male vocals in French. I have what I assume is their 3rd album, "Tertio." I like it a lot, and it appears to be available on CD on Amazon. Here is the one customer review:
Classic French Prog, December 26, 2001
Reviewer: Ben Miler (see more about me) from Lakeview, OR United States Atoll, along with Magma, Pulsar, and Ange, was one of the best known prog rock bands to come out of France. Tertio, originally released in 1977 on the EuroDisc label, was the third album by Atoll. Often compared to Yes, which I can't figure out why, because at least on this album, they don't sound much like Yes (I hadn't heard their previous two albums, so I can't comment there). The music here is symphonic prog as you expect from the late 1970s. The vocals are in French, but unlike, say Ange, the vocals here seem more easy to take in and not as intrusive. The keyboards are also as you expect from prog at this time: Mini Moog, string synth (in this case, the Eminent), and clavinet, with the rest of the instrumentation consisting of the usual (guitar, bass, drums). The opening song, "Paris, C'est Fini" starts off great, but it's my least favorite song here, because they sing about various big cities around the world (London, Bangkok, Tokyo, San Francisco, New York, etc.) which isn't what I really want to hear in prog rock. Luckily the rest of the album is much better, concluding in the ever wonderful "Tunnel". Though not my favorite prog album in my collection, it's still well deserving as a prog classic, and of your prog collection, and if you like such French prog bands as Ange, you're sure to love this.
Good luck.