In addition to Yes, Anderson appeared as a guest singer on "Lizard" by King Crimson for "Prince Rupert Awakes", the first part of their 23-minute title track recorded in 1970. He was chosen for the part as the desired vocal range was unattainable by the group's then-lead vocalist, Gordon Haskell. In 1974, Anderson co-wrote "Pearly Gates" with Iron Butterfly drummer Ron Bushy on the band's album "Scorching Beauty". This was followed by his first collaboration with Greek musician Vangelis, singing on "So Long Ago, So Clear", the last section of "Heaven and Hell Part I" on his 1975 album "Heaven and Hell".