 Conversely, academics Paul Hegarty and Martin Halliwell identify the Beatles, the Beach Boys, the Doors, the Pretty Things, the Zombies, the Byrds, the Grateful Dead and Pink Floyd "not merely as precursors of prog but as essential developments of progressiveness in its early days".At the time, critics generally assumed King Crimson's album "In the Court of the Crimson King" (1969) to be the logical extension and development of late 1960s proto-progressive rock exemplified by the Moody Blues, Procol Harum, Pink Floyd, and the Beatles.According to Macan, the album may be the most influential to progressive rock for crystallizing the music of earlier "proto-progressive bands ... into a distinctive, immediately recognizable style".