Karn Evil 9 is from the 1973 album, "Brain Salad Surgery". The song itself is divided into three movements. Karn Evil is an adapted spelling of the word carnival. The entire work is approximately 30 minutes long.
In the very beginning of the first movement, the lyrics refer to a warning"About an age of power no one had an hour to spare". This is a reference to the direction they see society moving. People are becoming obsessed with lots of things that don't matter and losing sight of the things that are important. There is reference to children being neglected.
The second half of the first movement is probably the group's most famous song, beginning with, "Welcome back my friends to the show that never ends..." This part of the song is a description of a carnival (karn evil) of the future. Each verse is an imaginary act in the carnival, much like the sideshows that happen in any carnival or circus. Some of the scenarios they sing about, such as blades of grass behind the glass imply that the world will no longer exist the way we know it.
Lyrics in the third movement possibly depict how the world is destroyed by nuclear war. There is reference to a [space]ship and a computer. Given how the entire song progresses, the `Evil' in the title shows how the evil (war) can destroy the world.
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