[Thor]

The early 70's put out so many great sounds
that it is hard to narrow it down..

1. Yes "Close to the Edge"-
the real epitomy of what progressive ment in the 70s rock scene, it tied with "Fragile" at this spot, a tough decision
2. King Crimson "In the Court of ..."-
progressive with bite for added measure
3. Genesis "Lamb Lies Down..."-
they hit their stride on this one, it tied with "Nursery Crime" at this spot, another tough call
4. ELP "Brain Salad Surgery"-
the title says it all, what a skullf**k
5. Renaissance "Ashes are Burning"-
Annie Haslam, what a voice what a band

If you want to talk about bands like Pink Floyd, Hawkwind, and Caravan; I believe you need to look into the psychadelic music genre that was coming out of the 60's, these fringe bands tend to get grouped in with progressive rock due to the experimental nature of the music/lyrics