the.com/progressive rock

means A rock subgenre from the late 1960s/70s that borrowed structures, instrumentation, and ambition from classical and jazz, favoring long compositions, odd time signatures, and concept albums over the standard three-minute single.

from The word 'progressive' here is used in the plain sense of 'advancing beyond what came before,' as bands like King Crimson, Yes, and Genesis pushed rock past its blues and pop roots into longer forms and stranger structures. The label was applied by critics and fans tracking this shift, not coined by any single person or moment — it simply named a trend already in motion, the way 'progressive' had earlier described jazz musicians stretching past swing-era conventions.