Continuing from Art Rock's post above, at least one thing that can be said for Prog is that it certainly does live up to its title in that it has "progressed" (in many cases, more so than other genres, although today's Metal is quite different from the 70s version). As we've been alluding to in another thread, Prog for some today may not necessarily mean the same thing to those of us brought up on the likes of
Krim,
Yes,
Genesis,
ELP,
Focus,
Curved Air, etc, etc, etc.
At the risk of getting philosophical and cliched, I'd hazard to say that Prog is related more to a concept rather than a time. For the less educated, Prog represents bombast, the "bigger is better" manifesto which personally I think is grossly misleading. Granted, I can see why the detractors could think like that, but it's only because they haven't looked deep enough.
For those of us who can be bothered, (and I think that would be most of us here) I feel that Prog is more to do with embracing diversity and inventiveness in every angle of production, from the composing and arranging of the music, through to the performance and recording, often with each of those elements incorporating an over-arching concept or theme.
I agree that a lot of recent (well, over the past 10 - 15 yrs anyway) Prog has taken on a Metal influence but without being exclusively so (one of the reasons I'm fond of
Porcupine Tree - they know when to give it a rest and move onto something else!
). However, there are also other genres that have had a look in with many other groups.
Mostly Autumn for example have a distinct folk edge whilst still attracting a significant "trad" Prog audience, as do
Whimwise.
Some "trad" Progheads I know have baulked at the mention of
Muse, but I for one, whilst acknowledging that they have a strong commercial appeal, also appreciate the many doffs-of-the-cap to Prog sensibilities that they inject into their material (and I don't think it can be refuted that they do).
Anyway, that's my take on it FWIW.
Cheers,
Matt