Lyric discussion by noisicus 

I think The Dark Side Of The Moon is about a compressed moment of epiphany experienced during a roller coaster ride .Before the music starts you can hear a click-click sound like the anti-rollback mechanism of a roller coaster when it is ascending a lift hill, followed by the sound of ecstatic screaming...And then, o boy, we lapse into the world of The Dark Side Of The Moon and philosophical ecstasy. This is consistent with the heartbeats;anybody who's ever ridden a coaster knows how the heart jackhammers just before and after a fall.

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