So someone tell me what this "Progressive Rock" is. I've heard it used to describe bands like Rush, Yes, Dream Theater, etc. but I have no idea what makes a band progressive. The term itself reminds me too much of "alternative" in that it's "alternative to what?" Well, what is "progressive" music progressing away from, and towards?

It so happens I'm a huge fan of Rush, Pink Floyd, and several other bands that have received this label. But I have no idea what it means. I hear it sometimes married to another label, "Art Rock." I've heard people say that it's rock that likes to push the envelope with unconventional keys, timings, and songwriting... But if you ask me, there are LOTS of bands which get artistic with their music (go beyond 4/4 timing, use strange tunings, write 15 minute songs, etc) that don't really get called Progressive. Is there some kind of distinctive sound or theme or pattern that these progressive acts fit into? Is there some canonical list of progressive rock bands out there that I'm not aware of?

I guess I just don't understand this category, and never have. Most recently, I've heard of one of my favorite metal-ish bands, The Gathering, referred to as "Progressive Metal." Like a combination of a Prog Rock and a Metal band. I'm not quite sure what to call them really (I have them as "Hard Rock" in my genres for lack of anything better) but this "progressive" label really confuzzles me.

Basically, to me, it sounds like a hoitey-toitey label for snobby music listeners to say that their music has "progressed" beyond pop music. I would argue that every one of these artistic bands has stayed very much on course with trends in pop music. Though sometimes these "progressive" bands have shaped pop music's direction, it was usually by accident, and I certainly don't think any of them just plain ignored pop music trends and wrote their music in a vaccum.

Anyway, I've never seen an adequate explanation of this term. Someone please help me out so I can rip my hair out over my unsatisfactory genre categorizations on my player.