Rime of the Ancient Mariner

Not strictly speaking a rock piece, this work started life as a children's opera but reached the world as a finished recording. The music mixes avant-garde and rock elements in what, by the standards of typical progressive rock, was fairly daring form -- the dissonant elements were challenging, and Robert Powell's narration demanded that the music be used for something more than listeners' druggy diversions. Most of it is engaging and diverting, and all of it makes Tubular Bells look amateurish by comparison.