Honourable mentions!
If any one of us had made a list of 10 albums, they would look different. Collaboration means compromise, so here are some honourable mentions to compensate for those that got squeezed out! I will add to this post in the future when/if I can be arsed.
King Crimson - In the Court of the Crimson King (1969)
The band King Crimson got famous before their debut album when they played a free concert in Hyde Park staged by The Rolling Stones in July 1969. The band blasted out a kind of music never heard before, jazz tinged and symphonically inspired rock, slightly reminiscent of Moody Blues, but much more sinister and with a musicianship that raised the bar for what a rock band should be able to do on a stage. Their debut album, In the Court of the Crimson King, was released just after. Exploring musical landscapes from the serene and beautiful to the chaotic and sinister, the album been celebrated as one of the most influential rock albums ever since. It also remains a favourite with KC fans and typically knife for the top spot with 1974 album Red. Just like Pink Floyd's Dark Side of the Moon, King Crimson's In the Court of the Crimson King is one of those albums every rock-interested person should check out, doubly so if they're interested in prog. Absolutely essential!
National Health - Of Queues and Cures (1978)
National Health was a Canterbury Scene supergroup started by keyboardists Dave Stewart (Egg, Hatfield and the North) and Alan Gowen (Gilgamesh). Early line-ups included Dirk "Mont" Campbell (Egg) on bass and Bill Bruford on drums (Yes, King Crimson), but for the band's second album, the drummer was Pip Pyle (Gong, Hatfield and the North) and John Greaves (Henry Cow) played bass and did some vocals. The band plays music reminiscent of Hatfield and the North on steroids, mixing complex rock compositions with expert musicianship. Compared to their jazzier debut, Of Queues and Cures is a rockier album with less improvisation and more rigid compositions. It is an album which features brilliant musicians at the top of their musical ability. Although the album may be daunting to newcomers to prog rock, those with an interest in the experimental and avantgarde may find Of Queues and Cures to be a highly addictive record. Absolutely brilliant!