As did just about every middle-class white American male a little too into literature and the arts, you better believe I had my progressive rock phase. Not that I don't still love prog and seek out new (old - please, nothing later than 1975) bands I haven't heard in the genre, but I mean, there was a time when I liked Dream Theater. I'm not embarrassed by the silly things I may have liked at any point in my life, because hey, at the time it was what I knew, and if I enjoyed it, that wasn't hurting anyone. E.g. I'm happy to admit to you that at age 13 I liked System of a Down and collected swords. But Dream Theater? Man, I was a college freshman for Cripe's sake, listening to some leather-fairy sing about teenage pregnancy and justifying it by telling people "you know he's an opera-trained singer?". I'll let you guess exactly how many friends that garnered.
Perhaps the most instantly recognizable element of prog is the sidelong epic - see, back in the oldie days when dinosaurs rode Jesus to get to their job at the fossil factory, record discs had recording on both sides, making for a natural division of the album into two halves - you had to stop listening at some point and flip the vinyl. If you listen to albums that were originally recorded in this format, you can usually pick out where the start/stop midpoint was from the pacing of the content. Starting in the year I don't know which, with I don't know what album, some probably British dude had the idea to put a long song, a "suite", on one side, and usually a handful of normal length radio-ready songs on the other. Hence we have the likes of Atom Heart Mother, 2112, Tarkus, and the works you'll find listed below. Some cRRAAAAAAAAZY artists even recorded double albums with multiple epics, like Yes on Tales from Topographic Oceans and Can on Tago Mago.
Side A looked like this... ...and Side B looked like this
Keep in mind that these are a completely different beast from prog's other calling card, the concept album. Epics have thematic unity, but don't always take the form of a narrative, and are (supposedly) composed in an emulation of classical style, including themes (musical), motifs, movements, whatever. I'm no music major, but you can see the difference between these and concept albums, which can be musically identical to non-concept albums (that is, how would you tell the difference between Captain Fantastic and Honky Chateau without the lyrics?).
Criteria time: a sidelong epic is a single song that takes up half of a vinyl. Songs not originally written for vinyl won't qualify, though none would have made it anyway. The rest of the album has nothing to do with my call - that's the only reason you might see ELP on here. I'm going to keep it to one per band and try to give you a little scope, and I think we're ready to begin. As usual, in no particular order.
Aw fuck, while researching this list I came across an annoying little trend. Since the epics usually left a little space on their side of the record, occasionally an extra one or two minute track is jammed in there, like "Pigs on the Wing Pt. 1" is thrown onto Side A of Animals along with the 17+ minute "Dogs". So I'm just going to ignore that and consider, for instance, "Dogs", as sidelong.
Come back tomorrow afternoon to check out the list!