“We were only talking the other day about the possibility that rock music – over the next 10 years – will really develop into a superior art form,” said Jon Anderson. Sounds in 1971, the year Yes released two progressive rock classics, The album Yes and Brittle. “Rock musicians will make music that will last much longer into the future.”

He was right on two levels. As bands like Yes, Genesis, and King Crimson flourished in the late ’60s and early’ 70s, adding classic structure and jazz chops to their amplified rock, their compositions began to literally swell: epic tracks like “Supper’s Ready” and “Close to the Edge” were long enough to warrant bathroom breaks.

But this period remains the genre’s golden age for a reason: before prog movements created tropes, before imitators went wild and diluted everything, these artists experimented without a rulebook.

This mess and savagery make prog a genre that’s hard to pin down. Symphonic prog, heavy prog, prog-pop, avant-prog, the Canterbury scene, RIO, Zeuhl, progressive electronics, folk-prog, jazz-fusion — at one point it’s almost easier to say what does not to qualify. And while the more traditional sounds of the genre have fallen into disuse, others have emerged from the indie and metal worlds, giving new life to the changing movement.

All of that to say: in some ways it’s easy to pick the top 50 progressive rock albums. Most of the entries near the top of our list are faultless. But also: It’s almost impossible. There are so many of them, in such varied styles, that you automatically exclude hundreds of essential titles by imposing an arbitrary number limit. Even if you don’t agree with some of these choices – and let’s face it, you will – we hope you approach our list as a platform for discovery. And isn’t “discovery” the goal of prog anyway?