First of all, let's establish our terms.
All -- and I mean ALL -- of what's called prog-rock completely sucks. The only thing it exists for is to remind you how great the real Beethoven and the real Yardbirds actually were.
That said, the one band who might be described as prog that is worth a fucking damn -- and it's more accurate to characterize them as classical-rock fusion -- is the stupdendously great Procol Harum.
Who achieved a seamless (and conceptually brilliant) melange of gospel (via Ray Charles organ/piano) and J.S. Bach.
And as an example, from their 1967 debut album, please enjoy their haunting -- and a song I've been trying to learn the piano part for, with zero success, over a period of 50 years -- "Salad Days (Are Here Again)."
And to every pretentious whey-faced British prog-rocker -- particularly Robert Fripp (aka the World's Most Boring Guitarist Who Isn't Frank Zappa) and anybody who ever played in Yes (with the exception of Rick Wakeman, who's a fun guy) -- please go fucking fuck yourself and your utterly sterile and soul-less music toot sweet. Thank you very much.
And may I add another fuck you to Robbie Robertson of The Band, who (in)famously said, when asked about Procol, that everything they did "was vaguely reminiscent of that Percy Sledge thing."
Fuck you, Robbie. Get back to me when anything you've ever done was as good as PH.
Have a great weekend, everybody!!!