Best art rock bands of the 70s

The middle 70’s were the golden years of progressive rock, when many bands reached their peak of popularity. Most of these groups were british and have released albums at that time still regarded as the greatest works of art rock. "The term art rock is sometimes used synonymously with progressive rock.[...] From 1972 to 1974 Genesis, King Crimson, ELP, and Yes (all of whom debuted in 1969–70) turned out ambitious suites that filled album sides.[...] Art rock had widespread appeal in its virtuosity and in the complexity of its music and lyrics, and it was intended primarily for listening and contemplation rather than for dancing.[...]" - Encyclopedia Britannica - www.britannica.com/. It’s somewhat hard to believe that such an intricate music style could be so easily found in the mainstream.