Well, there is an obvious trend among prog bands to have epic 20 min+ songs among their discography. Which prog epics do you know of? What do you think about them Etc...
The only ones I have are a bit obvious (kind of why I made this thread;to find more):
"Thick as a Brick" - Jethro Tull
"2112" - Rush
"Tarkus" - Emerson, Lake and Palmer
I've really been digging them lately, especially Tarkus (which I've played at least 3-4 times this week). I just love watching them flow in all sorts of wild directions (Thick as a Brick does this best) and the non-stop prog drums kick tons of ass as well.
It would be awesome to see the entirety of Thick as a Brick released as Rock Band DLC, haha.