What are the differences between progressive rock and post-punk?

Post-punk (usually) has less emphasis on instrumental virtuosity, even when it’s complex it tends not to be flashy about it. Also, I see prog-rock as being about adding complexity (and often eclecticism) to conventional rock music, while the more avant-garde post-punk tends to start by rejecting the more traditional trappings of rock and building on that. It comes from a deconstructive place, while prog tends to build on the past more. This is all subjective of course, but I think of it that way.

For me, what always struck me about the original prog movement (late 60s early 70s) was how regressive a lot of it was, in terms of taking clear influences from classical music.

At least, that applied to bands like later Deep Purple, ELP and Yes . It was as if they felt they were growing up, and that rock music - an infant genre in the late 1960s - was really just pop or blues music played loud, and was therefore somewhat immature. Popular music then was still in thrall to the singles charts, to bubble-gum ephemera, and they were desperate to separate themselves from that and stake out new territory. At the same time, the heavy blues basis of the late 60s rock bands was too backward looking.
So the prog bands wanted their music to gain some maturity, some artistic respect, some lasting value; but they felt the only way they could do that was hark back to "Serious" music and the classics. Of course it just made them sound pompous and pretentious.

Then you had Led Zep, who chose to go "backward to go forward" in a different direction, by reverting to various traditional folk and ethnic influences to expand their blues and soul palette. They certainly created some fresh and interesting new sounds, less stuffy than the prog-classical groups.

The jazz rock outfits like King Crimson had a better idea, in that jazz fusion was already pushing ahead from older jazz. It was challenging, complex, defiantly forward-looking.

Pink Floyd were the only big group of that era that were trying to take rock beyond its blues heritage without drawing (so overtly) on other older traditions (classical, jazz, blues or folk). Unfortunately, once they lost Syd, they ended up in a swamp of turgid power ballads with pompously didactic lyrics. (OK, some of it was quite good!)

It was the punk of the late 70s that attempted to get back to what had been truly revolutionary - "progressive" about 1960s rock music; albeit starting from a nostalgic view of the "Eden" before the "fall" represented by the hippie movement (the temptations of "artistic complexity"...). So the Ramones drew on surf music, and the Sex Pistols on bands like the early Who and Small Faces.

But in so doing they re-awoke rock as the music of adolescence (for a new generation of teenagers of course), but with the defiant attitude that being young and naive was nothing to be ashamed of. On the contrast, it was the ideal state of being, when one was truly alive, and the music expressed that perfectly: it was loud, it was short, it was simple, rhythmic and tuneful, it was demotic.

But also, it retained the musical revolution represented by the volume and timbre of the distorted guitar, that great discovery of the mid-60s. Extreme volume (to an immersive, visceral level) was a new musical effect, and guitar distortion an important new timbre. Originally employed in the service of the blues (the Very Loud Blues of Cream, Led Zep, Hendrix), now it was employed in the service of a bunch of shouty adolescents. But it still held a lot of promise for any future "progressive" movements in rock,

TBH, I'm not au fait with a lot of these generic pigeon-holes, and I'd have called Echo and the Bunnymen "new wave", although that's obviously no more precise than "post-punk". It hadn't occurred to me they were influenced by Genesis, although it makes sense. The guitar bands of that "post-punk" period were less embarrassed to take influence from the pre-punk prog era than the punks had been. It was as if once the decks had been cleared, once the old rock gods had been tipped off their pedestals, one could cherry pick from the remains in a more confident way - in a truly post-modern "bricolage" effect.

In short, I can't answer your last question! It's an interesting one - because obviously the differences between the genres which enable us to identify them in the first place must involve "compositional" elements, even if factors of production, arrangement and instrumentation are equally significant.

You summed it up pretty well. Obviously prog goes back a long way, not sure who's considered the originator although I hear shades of it in the Beatles. I'm also a big fusion fan, especially of Chick Corea and Mahavishnu Orchestra's. I'm fairly ignorant of post-punk I think, sorry.

IMO prog rock would have a cleaner comparison with post rock rather than post punk, but in either case, I think it has to do with form and structure more than anything. You’ll probably find recognizable structures in a lot of prog songs — verses, choruses, bridges, solo breaks, etc. They’re just augmented with more different sections in addition to the parts you’d see in a regular rock song. Although things can get pretty out there in prog, there’s usually a familiar sense of sequence, or a narrative arc, that shows us we’re listening to a rock song on a wider and more complex scale.

Post rock and post punk, by contrast, still use the tools of rock bands (guitars, amps, drums, vox, keys, studio techniques) and create comparable textures (kick drum and bass driving the beat, other instruments giving finer details of rhythm and harmony, etc.), but they don’t feel the need to replicate familiar sections and structures. You’ll rarely hear a post rock band play verse-chorus-verse-chorus-bridge-chorus like a rock band, or intro-verse-interlude-chorus-solo-verse-chorus-solo-bridge 1-chorus-bridge 2-verse-solo-chorus-outro like a prog band. Instead they feel free to be ambient, have verses of different lengths, not have discernible verses at all, etc.

That’s just my impression though, and I’m open to learning if I’m wrong. I’m not the most literate on post- genres.

TLDR: rock music is a house. Prog adds new rooms onto the house, post-punk and post-rock tear the house down and build something else with the pieces.

The differences are pretty clear imo. Prog-rock expands on its origins primarily in form, harmony, and meter. Post-rock is more about expanding on texture, space, and timbre

In the original prog movement, I think one common characteristic (though not necessarily in every prog band) is at least one virtuoso player, usually classically trained.

It's not anything against Post- punk but all things with "punk" in its name, means by definition it has a restricted harmonic usage below average, even for pop stardards.

On the other hand you got Prog which it's not the most complex genre ever (because there are baroque fugues, classical concertos and sonatas, hardcore Études, bebop jazz, atonal music, flamenco, etc...). But Indeed Prog is complexier than most of the popular music, and that's why it's not as popular.

For me the Post-Punk genre is nothing but a died pop trend reborned by post modern depressive world. Post - punk also is a melancholic genre whereas Prog can or not be, because the main focus is on making complex music just for the sake of it, and that's also my main critic because sometimes bands forgive to make audible music.

Post punk and Prog are antithesis by definition. Actually Post punk is more ralated to New Wave and Synth pop than to any other style of rock, and that's completely fine as long as you don't compare Joy Division with Emerson, Lake & Palmer, because any reasoned musician would say to you that that isn't even fair.

Stahp it

Post punk is like New Order, right? 80s "alternative" music was a smattering of genres, looking back.

I would say the post punk is like more creative rock, but prog has an intensity that rock doesn't have

Prog rock sucks and post-punk doesn't.