As the '70s blew over, progressive rock, the arguable king of all rock, gradually slipped from its peak.
Gone were the days of its mainstream phenomena. Instead, as the years rolled by, it moved into the world of cult fandom.
Despite the drop in recognition, a new generation of artists moved in, picking up where the likes of Pink Floyd, Rush, Jethro Tull and Yes left off.
As is customary with prog rock, new genres and musical scenes stepped in, blending the already-eclectic sound with everything from more jazz (King Crimson no doubt approved) to death metal. The result was an often darker, heavier side of the genre as it entered a phase commonly known as nu prog.
The results as the 21st century kicked off were mixed and varied. The genre know longer quite had the driving force and dominance of its heyday but instead spread out far and wide as its name and styling grew to diverse to completely nail down.
Overall, the noughties were an exciting time to be a prog fan. Everything from lighter, poppier melodies and concepts to ferociously grim, hard-hitting heavy metal-influenced riffs was on offer to enjoy.
10. Opeth - Blackwater Park
Stockholm's heaviest contribution to the prog world have time and again taken the genre to newer, angrier extremes.
'Blackwater Park', their fifth LP, saw the group plumb new depths of the extreme side of prog, mixing it with death metal for a startling but still technically sound vibe. It's a dramatic peak in the group's long and storied run, mixing extreme metal ideology with classic blues and jazz vibes. For metalheads, it was further vindication that heavy music can indeed live up to the technical wizardry of its artsier rock forbearers.
The titular track is a ferocious, 12-minute climax to a hybrid LP that gracefully jumps from strength to strength. It ultimately encapsulates everything that has come before it on the album, providing a perfect crescendo to the audio adventure the group have taken their listeners on.
Aided by Porcupine Tree frontman Steven Wilson coming in for the production, the group sift through suitably dark and macabre fare throughout. It's moody and unsettling but never lacking in intelligence or imagination.
At the time of its 2001 release, Blackwater Park left jaws on the floor throughout the prog and metal worlds alike. A perfect showcase of both intensity and innovation, it remains a seminal classic 21 years on.