Before Genesis became a pop juggernaut during the 1980s as a three-piece (Phil Collins, Mike Rutherford, Tony Banks), it was one of the pioneers of progressive rock with vocalist Peter Gabriel and guitarists Steve Hackett in tow. Perhaps the most acclaimed offering from those prog-rock years remains The Lamb Lies Down on Broadway (1974). Though not praised critically out of the gate, it grew in popularity over the years and is, perhaps, the defining moment of Genesis’ early days.

As we’ve seen so far, the British fancied the prog-rock movement. An unheralded group of the genre was London’s Gentle Giant. Active throughout the 1970s, the band was one of the more versatile and expansive progressive rock outfits. Gentle Giant’s sound included elements of folk, jazz, classical, medieval, and baroque stylings that set the group apart from its contemporaries. The band was quite busy back in the day, putting out 11 studio albums from 1970-80. Free Hand, from 1975, was its major-label release and the only one to crack the top 50 of the U.S. Billboard Album chart

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Between the lyrical and compositional complexity of guitarist Kerry Livgren’s mind to Robby Steinhardt’s rock-fused violin or Phil Ehart’s timely drumming, Kansas was more than just an arena rock staple from the 1970s. The band’s early work was filled with virtuosity, and even its breakthrough 1976 Leftoverture, anchored by the classic “Carry On Wayward Son,” was commercially progressive. There might not be a more progressive ballad than 1978’s “Dust in the Wind.”

King Crimson was founded in the late 1960s by guitarist/composer Robert Fripp and featured rock heavyweights such as Greg Lake, Bill Bruford, Boz Burrell, and John Wetton. Fripp and Co. were never afraid to experiment with their sound. Not only relying on the regular intricacies of prog rock, but classical, folk, and early elements of heavy metal that influenced the likes of Black Flag, Nirvana, and Mastodon. The band’s 1960 debut In the Court of the Crimson King remains one of the most influential albums in music history.

Words like innovative and creative don’t begin to define The Mars Volta. Rising from the ashes of At the Drive-In during the early 2000s, the band was always in search of something new. Principals Cedric Bixler-Zavala and Omar Rodríguez-López challenged themselves musically and lyrically. The Mars Volta sound has featured everything from psychedelic rock to hardcore, with the 2007 single “Wax Simulacra” winning the Grammy for Best Hard Rock Performance.

Many rock critics and fans will say that The Moody Blues were the true pioneers of progressive and art-rock. Most notably, with the release of 1967’s Days of Future Passed. That record features perhaps the most recognized and greatest prog-rock track of all time: “Nights in White Satin.” The song is like an orchestral musical dream that includes a spoken-word poem. The Moody Blues were so much more than that one hit and a major influence on fellow rock giants Deep Purple and Genesis.

The Floyd was an early staple within the British psychedelic rock movement. However, with the mental and emotional demise of longtime leader Syd Barrett and the addition of virtuosic guitarist David Gilmour, Pink Floyd headed in a more progressive direction (beginning with 1969’s Ummagumma). The Hall of Famers’ defining musical moment came with 1973’s Dark Side of the Moon, which is one of the great progressive rock albums ever recorded.

What pretty much started as a solo project for singer/guitarist Steve Wilson in the late 1980s, Porcupine Tree’s early music offered more of a nod to psychedelic rock — with a heavy Pink Floyd influence — of the 1960s. It wasn’t until the 2000s that the band shifted to a more progressive sound. Porcupine Tree didn’t enjoy true mainstream prog rock success until 2009 with The Incident, which won the Grammy for Best Surround Sound Album.

Like a few other bands on this list that broke out in the mid-to-late 1960s, England’s Procol Harum also fell into the psychedelic and art rock genres. There was always a classical element to the group’s collective sound, which was another trait of many progressive bands. Its 1967 hit single “A White Shade of Pale,” considered one of the best examples of the so-called baroque pop, made it to No. 5 on the U.S. Billboard Hot 100 and was a staple during the “Summer of Love.

From the beginning, this Seattle-area hard-rock/metal outfit seemed musically ambitious. With Geoff Tate’s high-pitched yet throaty voice, the band had a distinctive sound that carried the torch within the progressive metal genre for roughly three decades. In its classic form, the group was hailed for its conceptually creative lyrics, especially on Operation: Mindcrime (1988) and Operation: Mindcrime II (2006). Part of progressive metal’s “Big Three” with Dream Theater and Fates Warning, Queensryche drew some roundabout comparison to Pink Floyd thanks to the success of 1991’s “Silent Lucidity.”

If we were ranking the greatest prog-rock bands in music history, Rush would likely top the list based on its work in the 1970s. Heavy on lyrical conception, the legendary trio of Geddy Lee, Alex Lifeson, and Neil Peart offered various complex pieces (“2112,” “Cygnus X-1,” “La Villa Strangiato”) and themes often involving science fiction fantasy. Though a guitar-driven band at heart, Peart was widely considered one of the great drummers of all time. As a collective, Rush’s musical genius is hard to beat.

Led by the talented songwriters/composers Roger Hodgson and Rick Davies, Supertramp had progressive roots (most notably through its overly melodic self-titled debut). However, it did a relatively good job of putting some pop flare into the music. Beginning with 1974’s Crime of the Century, upon the band’s breakup, and with the Grammy Award-winning Breakfast in America (1979). The latter is arguably the most lyrically brilliant of any Supertramp release.

Whether positioned under the progressive rock or metal umbrella, there’s no denying the collective talent that has always been Tool. One of the more introverted, private groups in music history, Tool is a bit of an enigma from a persona standpoint. But its complex rhythms and time signatures, plus the stellar drumming of Danny Carey and mysterious vocal brilliance of Maynard James Keenan, have helped the band win four Grammy Awards and remain one of metal’s most acclaimed acts.

Another pioneer in progressive rock, Yes did a fine job of successfully mixing musicianship and showmanship. Armed with rock greats such as Bill Bruford, Jon Anderson, Chris Squire, Steve Howe, and Alan White over the years, the Hall of Famers were perhaps best known for their intricate instrumental pieces (check out “Cinema”) that showed off the individual talent of various band members. “Roundabout” from 1971’s Fragile captures the overall genius of the band, which enjoyed more commercial success with 1983’s 90125.