Progressive should be used to define a band who is searching to make something different, something not expectable. My aims in music, as in different aspects of art, obey to that rule. Of course there is another, many could simply make strange and ubiquitous noises, calling those NEW, REFRESHING, and COMPLETELY DIFFERENT.
But that's not music. Music must evoke feelings, music must come from the deepness of our soul. Classical composer's music persist precisely because of that.
Music without feeling soon is forgotten, even if in its era is mainstream. In my area of view, I've been observing that many people associate progressive to the experimental music made in the 70's and all the new bands that copy them. For me, those new bands are not progressive, but regressive.
My personal favourite rock bands are PORCUPINE TREE, OPETH, GODSPEED YOU!
